Development Board Choice
To be honest the RasPi is probably your best bet. Even if it is a little overkill the price is hard to beat. Other boards you may want to take a look at:

The Chumby Hacking Board,
Beagle Boards by TI,
Mbed by NXP

Or read through this article that discusses several interesting alternatives to RasPi: 

http://hackaday.com/2011/02/14/what-development-board-to-use-part-two/