Just picked up a Raspberry Pi Model B and thought you lot might be interested to know that it can be powered directly from the EV3 unit. I have the regular USB port on the EV3 plugged into the micro-USB power port of the Raspberry Pi and it boots fine and is even able to drive a keyboard, mouse and WiFi adapter.
Obviously this will drain the batteries very quickly, but I'm very excited as it allows me to give my robot a bigger brain without weighing it down with an extra battery pack and more cables.
I've just started playing with Raspberry Pi but I have plans to use it to control the robot by sending commands over USB. It will support other sensors like a camera in order to perform tasks like object detection using OpenCV to guide the robot towards areas of interest.
I'll update this thread with updates on my projects from time to time. If anyone has any ideas for interesting opportunities opened up by the Raspberry Pi then please discuss them here!