I am currently working with a few prototypes. One of those is the NanoFlyer board. It is tiny flight control board for small quadcopters. The board is based on the PiCopter by Frank Zhao with a few modifications. It has the ATMEGA128RF1 microcontroller chip with built-in low power 2.4GHz radio transceiver. There is ITG3200 gyro, BMA180 accelerometer and HMC5883L magnetometer on the board. The board measures 1 square inches in size. I got the pcb made at OSHPark.com, which is a community based pcb fabrication service and provides excellent quality boards at very affordable price if you are into small board designs. They charge $5 for per square inch and have about two weeks turn around time. I will post schematics and more information about the board later. Here are a few photos of the NanoFlyer v1.0 board:
This tiny board can easily be used to make other small robots like a self balancing robot and tiny autonomous robots etc. The board has all the digital and analog I/O pins exposed at the back of the board extending the possibilities to add more sensors and peripherals to the board.