Mine

So there are two places you can get any of these from: apple, or a cached copy at edgesuite. The first part of the url is:

http://appldnld.apple.com/ (normal downloads from apple)
http://pfd.apple.com/ (protected assets from apple)
http://appldnld.apple.com.edgesuite.net/content.info.apple.com/ (both, cached version)

Combine one of these with the url fragments listed below to create a full link.

You can't download a protected assets link without a download key. These change often.

For firmware not based on iOS there are three files: firmware image, signature file, and documentation file. Links are given for the firmware image, and the other two are in the same location. All three are listed for the first item, and the same pattern holds throughout. For iOS based devices, signature files are dropped and documentation requires a separate link, given afterward.

iPod (Scroll wheel) and iPod (Touch wheel) (aka first and second generations)
iPod/SBML/osx/bundles/061-2686.20060912.ipTsW/iPod_1.1.5.ipsw
iPod/SBML/osx/bundles/061-2686.20060912.ipTsW/iPod_1.1.5.ipsw.signature
iPod/SBML/osx/bundles/061-2686.20060912.ipTsW/iPodDocumentation_1.1.5.ipd

iPod (dock connector) (aka third generation)
iPod/SBML/osx/bundles/061-2687.20060912.IPwdC/iPod_2.2.3.ipsw

iPod (Click Wheel) (aka monochrome fourth generation)
iPod/SBML/osx/bundles/061-2691.20060912.ipDcw/iPod_4.3.1.1.ipsw
iPod/SBML/osx/bundles/061-2692.20060912.pODcW/iPod_10.3.1.1.ipsw

iPod Photo and iPod with color display (aka color fourth generation)
iPod/SBML/osx/bundles/061-2693.20060912.PdwCD/iPod_5.1.2.1.ipsw
iPod/SBML/osx/bundles/061-2694.20060912.ipDcD/iPod_11.1.2.1.ipsw

iPod (5th generation)
iPod/SBML/osx/bundles/061-2788.20061206.nS1yA/iPod_13.1.2.1.ipsw
iPod/SBML/osx/bundles/061-2965.20080313.R45jT/iPod_13.1.3.ipsw
iPod/SBML/osx/bundles/061-2789.20061206.9IIut/iPod_20.1.2.1.ipsw
iPod/SBML/osx/bundles/061-2966.20080313.2WqrT/iPod_20.1.3.ipsw

iPod (5th generation Late 2006)
iPod/SBML/osx/bundles/061-2790.20061206.iPr9t/iPod_25.1.2.1.ipsw
iPod/SBML/osx/bundles/061-2967.20080313.Cnvkg/iPod_25.1.3.ipsw

iPod classic
iPod/SBML/osx/bundles/061-3619.20070905.iNq3b/iPod_24.1.0.ipsw
iPod/SBML/osx/bundles/061-3877.20070914.n9gGb/iPod_24.1.0.1.ipsw
iPod/SBML/osx/bundles/061-3929.20071005.jGu6t/iPod_24.1.0.2.ipsw
iPod/SBML/osx/bundles/061-3940.20071115.0Iun5/iPod_24.1.0.3.ipsw
iPod/SBML/osx/bundles/061-4010.20080115.Ad4rF/iPod_24.1.1.ipsw
iPod/SBML/osx/bundles/061-4306.20080430.Gtr54/iPod_24.1.1.2.ipsw

iPod classic (120 GB)
iPod/SBML/osx/bundles/061-4962.20080909.Aaqs3/iPod_33.2.0.ipsw
iPod/SBML/osx/bundles/061-5740.20081111.ZaU7Y/iPod_33.2.0.1.ipsw

iPod classic 160 GB (Late 2009)
iPod/SBML/osx/bundles/061-6797.20090909.3uTfE/iPod_35.2.0.2.ipsw
iPod/SBML/osx/bundles/061-7155.20090925.Ju879/iPod_35.2.0.3.ipsw
iPod/SBML/osx/bundles/061-7299.20091217.Bghyt/iPod_35.2.0.4.ipsw

iPod mini
iPod/SBML/osx/bundles/061-2688.20060912.iDMni/iPod_3.1.4.1.ipsw
iPod/SBML/osx/bundles/061-2689.20060912.ipDmn/iPod_6.1.4.1.ipsw

iPod mini (2nd generation)
iPod/SBML/osx/bundles/061-2690.20060912.PdMin/iPod_7.1.4.1.ipsw

iPod nano
iPod/SBML/osx/bundles/061-2697.20061016.iPDnO/iPod_14.1.3.ipsw
iPod/SBML/osx/bundles/061-3190.20070315.p0oj7/iPod_14.1.3.1.ipsw
iPod/SBML/osx/bundles/061-3191.20070315.BgV6t/iPod_17.1.3.1.ipsw

iPod nano (2nd generation)
iPod/SBML/osx/bundles/061-3325.20070507.KnB7v/iPod_19.1.1.3.ipsw
iPod/SBML/osx/bundles/061-3326.20070507.0Pm87/iPod_29.1.1.3.ipsw

iPod nano (3rd generation)
iPod/SBML/osx/bundles/061-3878.20070914.P0omB/iPod_26.1.0.1.ipsw
iPod/SBML/osx/bundles/061-3930.20071005.94rVg/iPod_26.1.0.2.ipsw
iPod/SBML/osx/bundles/061-3941.20071115.Hngr4/iPod_26.1.0.3.ipsw
iPod/SBML/osx/bundles/061-4011.20080115.Gh5yt/iPod_26.1.1.ipsw
iPod/SBML/osx/bundles/061-4276.20080430.Gbjt5/iPod_26.1.1.2.ipsw
iPod/SBML/osx/bundles/061-5164.20080722.hnt3A/iPod_26.1.1.3.ipsw

iPod nano (4th generation)
iPod/SBML/osx/bundles/061-4637.20080909.vfH8i/iPod_31.1.0.ipsw
iPod/SBML/osx/bundles/061-5529.20080915.3ngi4/iPod_31.1.0.2.ipsw
iPod/SBML/osx/bundles/061-5583.20081111.Bhyui/iPod_31.1.0.3.ipsw
iPod/SBML/osx/bundles/061-5808.20090805.Fvgtr/iPod_31.1.0.4.ipsw

iPod nano (5th generation)
iPod/SBML/osx/bundles/061-7165.20090909.AzPKm/iPod_1.0.1_34A10006.ipsw
iPod/SBML/osx/bundles/061-7408.20091109.Kef5t/iPod_1.0.2_34A20020.ipsw

iPod nano (6th generation)
iPod/SBML/osx/bundles/061-9054.20100907.VKPt5/iPod_1.0_36A00403.ipsw

iPod shuffle
iPod/SBML/osx/bundles/061-2975.20061218.in8Uq/iPod_128.1.1.5.ipsw
iPod/SBML/osx/bundles/061-2953.20061218.yRet5/iPod_129.1.1.5.ipsw

iPod shuffle (2nd generation)
iPod/SBML/osx/bundles/061-3316.20070618.9n1bC/iPod_130.1.0.3.ipsw
iPod/SBML/osx/bundles/061-4376.20080303.Bi6T9/iPod_130.1.0.4.ipsw
iPod/SBML/osx/bundles/061-3317.20070618.nBh6t/iPod_131.1.0.3.ipsw
iPod/SBML/osx/bundles/061-4377.20080303.fk3ir/iPod_131.1.0.4.ipsw

iPod shuffle (2nd generation Early 2008) 2 GB
iPod/SBML/osx/bundles/061-4378.20080303.G5T87/iPod_133.1.0.4.ipsw

iPod Shuffle (3rd generation)
iPod/SBML/osx/bundles/061-6315.20090526.AQS4R/iPod_132.1.1.ipsw

iPod Shuffle (4th generation)
iPod/SBML/osx/bundles/061-8479.20100811.Cdf87/iPod_134.1.0.ipsw

iPod Touch
iPod/SBML/osx/bundles/061-3882.20070910.N8uyT/iPod1,1_1.1_3A101a_Restore.ipsw
iPod/SBML/osx/bundles/061-3932.20070927.p23dD/iPod1,1_1.1.1_3A110a_Restore.ipsw
iPod/SBML/osx/bundles/061-4036.20071107.9g3DF/iPod1,1_1.1.2_3B48b_Restore.ipsw
iPod/SBML/osx/061-4060.20080115.9Iuh5/iPod1,1_1.1.3_4A93_Restore.ipsw
iPod/SBML/osx/bundles/061-4312.20080226.Btu45/iPod1,1_1.1.4_4A102_Restore.ipsw
iPod/SBML/osx/bundles/061-4841.20080714.bgy8O/iPod1,1_1.1.5_4B1_Restore.ipsw
ProtectedAsset/iPod/osx/bundles/061-4957.20080711.Fr43E/iPod1,1_2.0_5A347_Restore.ipsw
ProtectedAsset/iPod/osx/bundles/061-4986.20080729.VftgP!/iPod1,1_2.0.1_5B108_Restore.ipsw
ProtectedAsset/iPod/osx/bundles/061-5243.20080818.039Ym/iPod1,1_2.0.2_5C1_Restore.ipsw
ProtectedAsset/iPod/061-5471.20080909.Plot5/iPod1,1_2.1_5F137_Restore.ipsw
ProtectedAsset/iPod/061-5356.20081120.Pt3ct/iPod1,1_2.2_5G77_Restore.ipsw
ProtectedAsset/iPod/061-5862.2009127.f2dke/iPod1,1_2.2.1_5H11_Restore.ipsw
ProtectedAsset/iPodTouch/061-6579.20090527.Xde3T/iPod1,1_3.0_7A341_Restore.ipsw
ProtectedAsset/iPodTouch/061-7161.20090909.VbuyJ/iPod1,1_3.1.1_7C145_Restore.ipsw
ProtectedAsset/iPodTouch/061-7266.20091008.SdLPn/iPod1,1_3.1.2_7D11_Restore.ipsw
ProtectedAsset/iPodTouch/061-7479.20100202.Secrc/iPod1,1_3.1.3_7E18_Restore.ipsw

iPod Touch (2nd generation)
iPod/SBML/osx/bundles/061-5494.20080909.8i9o0/iPod2,1_2.1.1_5F138_Restore.ipsw
iPod/SBML/osx/061-5358.20081120.Gtghy/iPod2,1_2.2_5G77a_Restore.ipsw
iPhone/061-5863.20090127.rt56K/iPod2,1_2.2.1_5H11a_Restore.ipsw
ProtectedAsset/iPodTouch/061-6581.20090527.PiKu7/iPod2,1_3.0_7A341_Restore.ipsw
ProtectedAsset/iPodTouch/061-7162.20090909.NkUy7/iPod2,1_3.1.1_7C145_Restore.ipsw
ProtectedAsset/iPodTouch/061-7269.20091008.Pfd32/iPod2,1_3.1.2_7D11_Restore.ipsw
ProtectedAsset/iPodTouch/061-7471.20100202.4itfh/iPod2,1_3.1.3_7E18_Restore.ipsw
iPhone4/061-7435.20100621.tr49t/iPod2,1_4.0_8A293_Restore.ipsw
iPhone4/061-8551.20100811.Xcder/iPod2,1_4.0.2_8A400_Restore.ipsw
iPhone4/061-7937.20100908.ghj4f/iPod2,1_4.1_8B117_Restore.ipsw

iPod Touch (3rd generation)
iPod/SBML/osx/bundles/061-7163.20090909.NtstR/iPod3,1_3.1.1_7C145_Restore.ipsw
iPhone/061-7238.20090918.23GhT/iPod3,1_3.1.1_7C146_Restore.ipsw
iPhone/061-7271.20091008.Tch23/iPod3,1_3.1.2_7D11_Restore.ipsw
iPhone/061-7473.20100202.4i44t/iPod3,1_3.1.3_7E18_Restore.ipsw
iPhone4/061-7381.20100621.AzSP9/iPod3,1_4.0_8A293_Restore.ipsw
iPhone4/061-8554.20100811.Bgt54/iPod3,1_4.0.2_8A400_Restore.ipsw
iPhone4/061-7941.20100908.sV9KE/iPod3,1_4.1_8B117_Restore.ipsw

iPod Touch (4th generation)
iPhone4/061-8490.20100901.hyjtR/iPod4,1_4.1_8B117_Restore.ipsw

iPhone
iPhone/061-3538.20070629.B7vXa/iPhone1,1_1.0_1A543a_Restore.ipsw
iPhone/061-3614.20070731.Nt6Y7/iPhone1,1_1.0.1_1C25_Restore.ipsw
iPhone/061-3823.20070821.vormd/iPhone1,1_1.0.2_1C28_Restore.ipsw
iPhone/061-3883.20070927.In76t/iPhone1,1_1.1.1_3A109a_Restore.ipsw
iPhone/061-4037.20071107.5Bghn/iPhone1,1_1.1.2_3B48b_Restore.ipsw
iPhone/061-4061.20080115.4Fvn7/iPhone1,1_1.1.3_4A93_Restore.ipsw
iPhone/061-4313.20080226.Sw39i/iPhone1,1_1.1.4_4A102_Restore.ipsw
iPhone/061-4956.20080710.V50OI/iPhone1,1_2.0_5A347_Restore.ipsw
iPhone/061-5135.20080729.Vfgtr/iPhone1,1_2.0.1_5B108_Restore.ipsw
iPhone/061-5246.20080818.2V0hO/iPhone1,1_2.0.2_5C1_Restore.ipsw
iPhone/061-5202.20080909.gkbEj/iPhone1,1_2.1_5F136_Restore.ipsw
iPhone/061-5779.20081120.Pt5yH/iPhone1,1_2.2_5G77_Restore.ipsw
iPhone/061-5830.20090127.Mmni6/iPhone1,1_2.2.1_5H11_Restore.ipsw
iPhone/061-6580.20090617.XsP76/iPhone1,1_3.0_7A341_Restore.ipsw
iPhone/061-6974.20090731.Cf4Tg/iPhone1,1_3.0.1_7A400_Restore.ipsw
iPhone/061-6605.20090909.PQ3ws/iPhone1,1_3.1_7C144_Restore.ipsw
iPhone/061-7268.20091008.32pNe/iPhone1,1_3.1.2_7D11_Restore.ipsw
iPhone/061-7481.20100202.4orot/iPhone1,1_3.1.3_7E18_Restore.ipsw

iPhone 3G
iPhone/061-4955.20080710.bgt53/iPhone1,2_2.0_5A347_Restore.ipsw
iPhone/061-5134.20080729.Q2W3E/iPhone1,2_2.0.1_5B108_Restore.ipsw
iPhone/061-5241.20080818.t5Fv3/iPhone1,2_2.0.2_5C1_Restore.ipsw
iPhone/061-5198.20080909.K3294/iPhone1,2_2.1_5F136_Restore.ipsw
iPhone/061-5778.20081120.Aqw4R/iPhone1,2_2.2_5G77_Restore.ipsw
iPhone/061-5828.20090127.aQLi8/iPhone1,2_2.2.1_5H11_Restore.ipsw
iPhone/061-6578.20090617.VfgtU/iPhone1,2_3.0_7A341_Restore.ipsw
iPhone/061-6972.20090731.Zx3Rr/iPhone1,2_3.0.1_7A400_Restore.ipsw
iPhone/061-6600.20090909.AwndZ/iPhone1,2_3.1_7C144_Restore.ipsw
iPhone/061-7265.20091008.Xsd32/iPhone1,2_3.1.2_7D11_Restore.ipsw
iPhone/061-7468.20100202.pbnrt/iPhone1,2_3.1.3_7E18_Restore.ipsw
iPhone4/061-7436.20100621.58Yt4/iPhone1,2_4.0_8A293_Restore.ipsw
iPhone4/061-8616.20100715.phnt4/iPhone1,2_4.0.1_8A306_Restore.ipsw
iPhone4/061-8802.20100811.XcfpR/iPhone1,2_4.0.2_8A400_Restore.ipsw
iPhone4/061-7932.20100908.3fgt5/iPhone1,2_4.1_8B117_Restore.ipsw

iPhone 3GS
iPhone/061-6582.20090617.LlI87/iPhone2,1_3.0_7A341_Restore.ipsw
iPhone/061-6976.20090731.Vgbt5/iPhone2,1_3.0.1_7A400_Restore.ipsw
iPhone/061-6609.20090909.mwws4/iPhone2,1_3.1_7C144_Restore.ipsw
iPhone/061-7270.20091008.phn32/iPhone2,1_3.1.2_7D11_Restore.ipsw
iPhone/061-7472.20100202.8tugj/iPhone2,1_3.1.3_7E18_Restore.ipsw
iPhone4/061-7437.20100621.5urG8/iPhone2,1_4.0_8A293_Restore.ipsw
iPhone4/061-8618.20100715.Zapn4/iPhone2,1_4.0.1_8A306_Restore.ipsw
iPhone4/061-8805.20100811.Dcr4e/iPhone2,1_4.0.2_8A400_Restore.ipsw
iPhone4/061-7938.20100908.F3rCk/iPhone2,1_4.1_8B117_Restore.ipsw

iPhone 4
iPhone4/061-7380.20100621,Vfgb5/iPhone3,1_4.0_8A293_Restore.ipsw
iPhone4/061-8619.20100715.4Pnsx/iPhone3,1_4.0.1_8A306_Restore.ipsw
iPhone4/061-8807.20100811.3Edre/iPhone3,1_4.0.2_8A400_Restore.ipsw
iPhone4/061-7939.20100908.Lcyg3/iPhone3,1_4.1_8B117_Restore.ipsw

iPad
iPad/061-7987.20100403.mjiTr/iPad1,1_3.2_7B367_Restore.ipsw
iPad/061-8282.20100713.vgtgh/iPad1,1_3.2.1_7B405_Restore.ipsw
iPad/061-8801.20100811.CvfR5/iPad1,1_3.2.2_7B500_Restore.ipsw

documentation files for iOS:

ipod:
1.1?
1.1.1?
1.1.2?
1.1.3?
iPod/SBML/osx/bundles/061-4354.20080226.Bk439/iPodDocumentation_1.1.4.ipd
iPod/SBML/osx/bundles/061-4984.20080714.XsEW6/iPodDocumentation_1.1.5.ipd
iPod/SBML/osx/bundles/061-4721.20080711.Vgt6I/iPodDocumentation_2.0.ipd
2.0.1?
iPhone/061-5339.20080818.nHlp4/iPodDocumentation_2.0.2.ipd
2.1?
2.2?
iPod/SBML/osx/061-5928.20090127.ZaspL/iPodDocumentation_2.2.1.ipd
3.0?
3.1.1?
3.1.2?
iPhone/061-7821.20100202.AzPyt/iPodDocumentation_3.1.3.ipd
iPhone4/061-8460.20100621.BgR5r/iPodDocumentation_4.0.ipd
iPhone4/061-8877.20100811.Fvgrt/iPodDocumentation_4.0.2.ipd
iPhone4/061-9059.20100901.AzW3P/iPodDocumentation_4.1.ipd

iphone:
1.0.0?
1.0.1?
iPhone/061-3823.20070821.vormd/iPhoneDocumentation_1.0.2.ipd
1.1.1?
iPhone/061-3992.20071107.3Fvgd/iPhoneDocumentation_1.1.2.ipd
1.1.3?
iPhone/061-4355.20080226.Pt57h/iPhoneDocumentation_1.1.4.ipd
iPhone/061-4722.20080710.Vf0pW/iPhoneDocumentation_2.0.ipd
2.0.1?
iPhone/061-5340.20080818.VB9iU/iPhoneDocumentation_2.0.2.ipd
iPhone/061-5390.20080909.azsw3/iPhoneDocumentation_2.1.ipd
2.2?
iPhone/061-5920.20090127.vgrt5/iPhoneDocumentation_2.2.1.ipd
iPhone/061-6592.20090612.0O8nr/iPhoneDocumentation_3.0.ipd
iPhone/061-6994.20090731.Dci8U/iPhoneDocumentation_3.0.1.ipd
iPhone/061-7111.20090909.PTgdK/iPhoneDocumentation_3.1.ipd
3.1.2?
iPhone/061-7822.20100202.VfP8u/iPhoneDocumentation_3.1.3.ipd
iPhone4/061-8461.20100621.Plhn4/iPhoneDocumentation_4.0.ipd
iPhone4/061-8694.20100715.pn4nr/iPhoneDocumentation_4.0.1.ipd
iPhone4/061-8878.20100811.VPlku/iPhoneDocumentation_4.0.2.ipd
iPhone4/061-9060.20100901.Mr5YT/iPhoneDocumentation_4.1.ipd

ipad:
iPad/061-8481.20100713.txd34/iPadDocumentation_3.2.ipd
3.2.1?
iPad/061-8879.20100811.AsWe3/iPadDocumentation_4.0.2.ipd (this is 3.2.2 for some reason)