With the release of Ubuntu Touch images for the Nexus devices and the source code last week, we knew that ports for various devices would start coming up soon. Ubuntu touch has been ported to the Samsung Galaxy S2 I9100 (please do not try to flash it on other versions).
Please note if you flash the build it will wipe ClockworkMod Recovery (or any other custom recovery you have), and you cant transfer files to the phone. so make sure you have a PC, This will also bring back the Triangle of Evil. To re-install CM or AOSP or any other ROM, you will need to use Odin or Heimdall.
For download links and installation instructions head over to the original thread on xda developers.