Datalogger shield for the Arduino. Uses the FTDI Vdip 1 module to read/write to a standard USB stick. The shield samples 4 analogue inputs measuring voltage/currents, has a Real Time Clock (RTC), temperature sensor and power saving circuitry.
I currently use it to record data from my solar power system. Some details here: http://www.ianstedman.co.uk/Microcontroller_bits_n_pieces/Arduino/Arduino_datalogger/arduino_datalogger.html
My first release of the datalogger software is included. I used an Androino DIY clone for the host board, hacked to use a higher efficiency switchmode supply.