A new UAV/ MAV optical flow sensor has been released over at DIYdrones.   This sensor will mainly be used for Arducopter Multi-rotor and traditional helicopters to improve position hold.  This sensor is based on the ADNS3080 mouse sensor, and features a 8mm leans with 11deg FOV, ideal for low altitude position hold functions.

A library to use this sensor can be found here
This board has an SPI interface so it can be interfaced to many other micro controllers.
This optical flow sensor is also for sale in the UK from UnmannedTech

The much anticipated ArduIMU+ V3 is available for pre order in the UK. The final version of the board is in production and will be shipped within the next week.

Documentation and example IMU code are almost complete and will be released as they become available.  On a side note, this board is not a replacement for the OilPan IMU shield for ardupilot mega.

A new version of the ArduIMU series is going to be stocked very soon.  The ArduIMU v3 is the latest in the low cost and small IMUs which is arduino compatible (ATmega328 @16Mhz).This IMU includes the new MPU-6000 which has a tripple axis accelerometer and gyro built in.  The MPU-6000 also takes care of sensor fusing with 24bit ADC sampling.  This IMU also includes the HMC-5883L tripple axis magnetometer. You can use this for many applications that require motion measurement, such as a multi-rotor helicopter, model rockets, and many other robotics applications. 
Read more for the full feature list.