SWITCHcast is a sophisticated video management system, by means of which lecturers can very simply record their lectures, upload them to a central server, post-process them and make them available to students via the internet - both as online streams and as downloads for offline use.
Jahshaka is a video and film compositing, editing and special fx system that uses OpenGL & OpenML hardware rendering to give operators real time interactivity. The system is cross platform, and also includes full CG, paint and image processing modules.
HandBrake is a GPL'd multiplatform, multithreaded DVD to MPEG-4 ripper/converter. HandBrake was originally available on the BeOS, but now has been ported over to MacOS X