Parallax has a new MCU module optimized for robotics that looks pretty cool.
The Propeller Robot Control Board provides all the necessary base circuits needed to build a very powerful mid-size robotics platform. The control board has an on-board USB serial interface to facilitate programming and communication with the Propeller chip. A dual switching supply regulates 6.5 – 20 VDC input to 3.3 V and 5 V at up to 3 A and contains green and red LEDs to indicate proper operation or an under-voltage condition. The on-board dual H-bridge motor driver makes it possible to directly drive DC motors up to 2.8 A and 20 V. The 24 available I/O pins are buffered through three 8-bit bidirectional voltage level translators providing direct 5V interface capability. The input voltage can come from a battery pack or a wall adapter using a standard 2.1mm barrel plug.
The 24 available I/O pins are connected to three TXB0108 8-bit bidirectional voltage level translators. They convert the voltage from 3.3V at the Propeller chip to 5V at the servo headers. These pins are fully bidirectional and are grouped as three ports with eight I/O lines each. Each group is brought out to a set of servo headers. A jumper selects either 5V or VIN for the group. All data pins on the servo header are at 5V signal levels, however should the need arise to directly access the Propeller chip I/O for 3.3V interfacing, solder points are provided to disable the translators and gain direct access to the I/O pins.
It retails for $100.