I got an ADK board about 2 months ago but I just started to play with it a couple of days ago. Two days ago I posted two tutorials on my website:
How To Send Data From Your Android Device to The ADK Boardhttp://allaboutee.com/2011/12/31/arduino-adk-board-blink-an-led-with-your-phone-code-and-explanation/
How To Send Data From The Board To The Android Devicehttp://allaboutee.com/2011/12/31/arduino-adk-board-how-send-data-from-the-board-to-the-android-device/
Unfortunately I didn't buy the board the with the sensors so I had to basically trim down the code to what it was only necessary for communication. What I have to say is that Arduino+Android projects are not for beginners, you have to know Java well or there won't be much you can do other than copy and paste other people's projects, that's for the Android-side code, the Arduino side code is not complicated at all.