Connectix Virtual Game Station (9) - PS One emulator.
Makes you feel like you're in a Bugs Life. I always see it as open source on Linux so there might be an OS X build It's pretty awesome, logical puzzle game. I have copies if you can't find it online and are interested Just plug in a usb controller and go to town I'm not sure how well it will run on a g3, but I have a copy on a g4 machine running Leopard if you'd like it-I can't find any ppc versions of it anymore to download) (DXX-rebirth is a 'modern' opensource remake. As for places to find them, check out magintoshgarden.Some of my favourites are as follows:
