The early preview build of CM10 for the GSIII has been released, and is now ready for you to try out Jelly Bean on that awesome Galaxy S III of yours! It’s in a very early state, so you won’t be seeing a lot of CM9′s features merged over yet, but hopefully soon.
Here are the known issues so far (as stated by Cyanogen):
Overlay for UI (extra butter)- We're waiting on CodeAurora to publish, UI is a little janky.
Camera preview turns green during animations and may crash.
All the things (LOL)
Remember guys, these are very early preview builds, so DON’T expect perfection. The AT&T ROM can be found here, the T-Mobile ROM here, and the Sprint ROM here. Be sure to follow the exact instructions, and PLEASE MAKE A NANDROID BACKUP BEFORE FLASHING.