This site has a good selection of guitar electronics like pickups, pots, switches, etc... at some of the lowest prices I've seen. They also have lots of helpfull wiring diagrams.
There is only one problem I had with the site. Although it's easy to navigate and all that, the site has an amatuer look to it. This made me kind of afraid to order from them until I checked them out (see my post in their guest book here.)
and is the only reason I rated them 4 stars instead of 5.