Something

SELECT *
FROM [Item], [Category], [Bid] 
WHERE [Item.category_id] = [Category.category_id] 
AND [Item.seller_id] = ?
AND [Bid.item_id] = [Item.item_id]
AND [Bid.bid_id] = 
    (
    SELECT MAX([bid_id]) 
    FROM Bid b2 
    WHERE [b2.item_id] = [Item.item_id]
    )