Sparkfun has just released an "9DoF" Razor IMU board
($125) with an Atmega328, three flat gyros, a three-axis accelerometer and a three-axis magnetometer (no GPS input). This is basically similar to the ArduIMU+, but designed for indoor use or other places where GPS is not available or desirable. Because the Atmega runs at 16 Mhz, it's Arduino compatible.
We've been working with them on this board, and will be converting the ArduIMU+ code to work with it soon; it will be available on the Sparkfun site and here. Stay tuned!