Handgun Information Page - Lots of articles and information on guns, cartridges and weapons in general.

Revolver Cartridges - A bit of information on them.

List of Cartridges by Type - A great list with lots of info on different cartridge types.

A great page for pictures and cutaways as well as descriptions of bullet types:

http://matrix.dumpshock.com/raygun/basics/bullets.html