9 - "Ultimate" version - Trivia Track, Easter Eggs, Bonus Features, better video quality if you have a super-high end TV.
5 - "Semi-Ultimate" version - Trivia Track, fewer Bonus Features, no Easter Eggs. Decent quality for most people.
5 Purist - Undoes some more hotly debated changes - some editing, no added music. Barebones, no menus, no trivia, no bonus, no eggs, nothing.
Xvid - "Workprint" version - still had some FX issues and other tweaks that slipped through and were fixed on the 5 and 9 versions.
Purist is only available in NTSC, everything else comes in NTSC or PAL, I believe.