Owners of the Galaxy S III that love modding, keep your eyes open as you read this because an unofficial ClockworkMod has released for the device. The person who created a root method for the GS3 without actually having the device in his hand chainfire on XDA is the one to also brought this CWM to the public. Keep in mind this isn’t a complete version, users have reported it to work but it’s still being tested for bugs, furthermore by trying to flash CWM on your device you could permanently damage it, do so at your own risk. For the instructions and necessary files, click the second source link.
Source: XDA-Developers, XDAForums