College of Musical Arts Trumpet Page - This site has some good information about trumpet playing with a few sound files on the side.
Ken's World - This page has pictures and info on great players such as Dizzie Gillespie.
Bassist's Home Page - This isn't a trumpet link, but it is a good music link with original compositions.
Tim's Page - Tim has a lot of info on classical composers, talented violinists, and many good MIDI sound files as well.