Here's the lists for the do-it-yourselfers. Most Chopper Shops have a line of their own custom designed parts available through their site or specific catalogs. I've tried to keep this list to the sites of the manufacturers of parts that don't build bikes (catolog sites are in a sub-list to the left).
At this point, the sites are listed alphabetically as opposed to by the products offered but, you can pause your cursor over the link and a small window will tell you what kind of parts they offer (depending on your browser).