Instructables
Launchpad is a Texas Instruments microprocessor based development board that is a very low cost "alternative" to arduino. 

The Launchpad costs$4.30 and features:

On-board Emulation
The MSP430 LaunchPad features on-board emulation, which means you can program and debug your projects without the need for additional tools.

BoosterPack-compatibility
All pins of the MSP430G2 device are fanned out for easy access. These pins make it easy to plug in 20-pin BoosterPacks that add additional functionality like wireless, capacitive touch & more

Supports MSP430G2xx MCUs
The MSP430 LaunchPad supports MSP430G2xx Value Line MCUs. These devices go up to 16MHz, feature up to 16kB Flash & 512B RAM. They also offer integrated ADCs, timers, serial communication modules & more.

(Source http://www.ti.com/ww/en/launchpad/msp430_head.html)