I recommend looking at the CELLv1 from SparqEE[1] if anyone is looking for a nice development board for RaspberryPi/Arduino. It supports 3G, not only GPRS as most of the other GSM boards available.

I received mine a few weeks ago and have been having loads of fun working with it.

[1] http://www.sparqee.com/portfolio/sparqee-cell/