The folks on the CyanogenMode team have been really working quick. Their custom CM9 version of ICS already supports the U.S. Samsung Galaxy S III before it even launches in the United States. Of course, it shouldn't be too surprising to find out that CM9 is out for the phone considering two very important key details. One, the international version of the phone has been out for a while now. Two, Steve "Cyanogen" Kondik actually works as a software developer for Samsung now. Yep, it's pretty safe to say he has an insider track.
Here's a link below at XDA to the CM9 nightly builds, and here is a quote with some details about what CM9 adds, and what still doesn't work quite right yet:
Source: HotHardware and XDASome of the features included are lockscreen gestures, incognito browsing mode, OpenVPN, a DSP equalizer, and themes support, to name a few. There are also some known issues, such as the FM radio not working, wonkiness using the camera's LED flash (could cause an annoying force close), and waking up the device using volume keys may not work properly.