In the mean time you can use the $25 USB Host shield that Sparkfun already sells.
http://romfont.com/2011/05/12/google%E2 … -hardware/
Personally this is my favorite board so far:
http://diydrones.com/profiles/blogs/new … t%3A370646
Finally, note that Sparkfun is already selling IOIO, which can easily be made to support the ADK standard as well. I’m sure Ytai is working on that.