Also, if you have an older G3 mac, XinePlayer for G3 can sometimes play movies that Quicktime and VLC won't. http://developer.berlios.de/project/...?group_id=3329

More tips (adds the XVID codec) at http://www.insaneness.com/xvid.html
Needed to play the free movies at http://www.welcometothescene.com/download.shtml for example.