Texas Instruments has introduced a cheap and easy to use development tool based on the MSP430 microcontroller. LaunchPad is intended for beginners and experienced users that want to create microcontroller-based applications. The Launchpad kit includes a development board, 2 programmable MSP430 micrcontrollers and a mini USB cable. A good place to start is the Launchpad wiki and you can buy it from the TI-eStore or Mouser. Shipping is free from TI!
TI MSP430 Launchpad for $4.30 - [Link]