I’ve recently discovered the stm32-discovery board from STMicroelectronics thanks to someone at work.  It’s quite an impressive device (the STM32F100RB onboard, that is), but not as easy to use out of the box as an Arduino.

http://www.st.com/internet/evalboard/product/250863.jsp

I bought two from mouser at $11 a piece….expect to see several upcoming posts related to this little board.