A few months back I made a very simple Kiwi drive robot for a larger project, which has now been sitting on the back-burner for a while. I figured that it was high time I did something with it, so I wrote up a quick post explaining how I made it as well as the source code.
http://upnotnorth.net/2011/07/10/kiwii/
It's definitely not a "complete" project, but it's awfully fun to play with and hopefully it'll be useful to someone. Enjoy!