I’m sort of surprised nobody else has made something like these SmartJoy FRAG adapters to let you use PS2 and USB mice and keyboards on your Xbox or Playstation 2. The thing is, I’m fairly sure that each game will have to have mouse drivers included—I don’t think they’re inherent to the game consoles themselves. I could be wrong, though, and it would certainly be strange for them to release something that had little-to-no chance to work. They’re only $30 or so from Lik-Sang, so I’ll let you guys be the guinea pigs and let me know when they ship later this month.
Console FPS Frags with own Keyboard/Mouse Combo For Xbox and PS2 [ModernJackass]