The Raspberry Pi Foundation has started shipping Gertboard, which is a extension of Raspberry Pi that can be used to control several real life devices. According to the official announcement, people can hack it and use it to control lights, use it to run motors or sense lights, heat etc.
Here are some pictures of what the GertBoard looks like:
The default model ships with 512 mB of RAM. You can order Gertboard from Farnell, it costs 29.19 pounds in United Kingdom.