Something

RewriteEngine on
RewriteLog /usr/local/apache/logs/rewrite.log
RewriteLogLevel 9
RewriteMap      lc              int:tolower
#if www.example.com or example.com end and go to www.example.com/example.com
RewriteCond   %{HTTP_HOST}                 ^(www\.)?example\.com$ [NC]
RewriteRule   ^(.+)             - [L]

#if www.foo.example.com 301 to foo.example.com - THIS ONE'S IMPORTANT
RewriteCond   %{HTTP_HOST}                 ^www\.([^.]+)\.example\.com$ [NC]
RewriteRule ^(.*)$ http://%1.example.com$1 [R=301,L]

#these last 3 lines are to rewrite foo.example.com/something to www/example.com/foo/something
RewriteCond %{HTTP_HOST} ^([^.]+)\.example\.com$ [NC]
RewriteCond %{REQUEST_URI} !^/icons
RewriteRule (.*) /www/example.com/${lc:%1}$1