Sorry here is the link SparkFun 6 Degrees of Freedom IMU Digital Combo Board - ITG3200/ADXL345 - SEN-10121 - SparkFun Electronics
I feel pretty comfortable with this IMU. I have been reading a lot about it and have already found several examples of code to get the data that I need. I have been using arduino for about a year now so I feel pretty confident with my ability to get the board working. I am not as familiar with I^2C as I should be but I am reading and working on it now.
My main concern is the motors. I know that selecting the proper motors and wheels will make or break the project. Ultimately I am thinking I need something with a lot of torque that can respond quickly. I don't think I need high rpm, but it must spin fast enough to catch up with itself when falling.
Possibly this type of motor with the encoders. http://www.robotshop.com/12v-gear-motor-encoder.html
Also correct me if I am wrong, but I am thinking something around a foot to foot and a half tall with the center of mass being around the motors. From what I am reading the IMU needs to be near the top?