Put one of those old cellphones lying around to good use.
Most people have at least one or two old cellphones sitting in a drawer somewhere. Now you can use one for your next Arduino project. Alex of insideGadgets has kindly posted a detailed tutorial showing how to hack and old Nokia 6110 (or any derivative) to send text messages from an Arduino. Even if you don’t have one of these sitting around, old technology (aka project materials) can be bought at absurdly low prices.
Via Arduino blog