Devs have released the first experimental CyanogenMOD 9 build for Samsung Galaxy S2. This build is highly unstable and is in no way meant for normal users. According to the devs working on making CM9 work on SGS2, overall CyanogenMod is under very heavy development right now including the device specific parts for Galaxy S II, and they would be able to release stable ROM only by Jan or February 2012.
If you are an advanced user and want to have a feel of the build, you can grab the download right now from XDA thread. You will to be able to flash it using ODIN or via CWM, detailed instructions are available at thread.
Known Issues with the build:
- RIL crashes on providers with NITZ, button backlight issues, low haptic feedback, sensors bugs, video recording problems, YouTube video playback is black, missing video codecs and a lot of other stuff.