There are 3 repositories under atari-falcon topic.
A large repository of Atari ST (and family) source code
Atari ST version of the replay source for Arkos Tracker 2 (http://www.julien-nevo.com/arkostracker/)
Web-based tool to build gradient data for retro platforms using a visual editor
Sprite generator for the Atari ST and compatibles, hopefully not sucking much