I found a fantastic site dedicated to free arrangements of baroque and renaissance music:
WIMA: Werner Icking Music Archive - Composers and Editors
There a ton there for trumpet.
PS does anyone have a D trumpet part to the Corelli Sonata? I have lost mine.. Also, the Richter on the site: Werner Icking Music Archive: Franz Xaver Richter is only a C part. Does anyone have Finale and want to post a transposed D part?