I just posted a tutorial on the Silicon Valley HomeBrew Robotics Club Wiki entitled Installing Ubuntu With Real Time Patches On The PandaBoard. In addition to instruction for installing Ubuntu from scratch, which is also described in my recent post on ozbotz.org, the tutorial explains how to compile a new kernel from source and test the latency of the OS.
If you disassemble a Chumby One, you will find that is contains an easily accessible TTL serial port. This article shows you how to turn the serial port TX and RX signals into PWM outputs.
The Chumby contains a very capable accelerometer, the Freescale MMA7455. However, the accelerometer daemon running on the Chumby is not optimzed for applications that need rapid updates from the accelerometer. This article explains how you can write C code that unlocks the full potential of the Chumby accelerometer.