The Raspberry Pi is the newest thing to hit the world of programming and it is going to be big. At the moment it is a bit inaccessible to students unless they are at KS4 level computing. However this will not always be the case as the Rapsberry Pi is being developed so that it is fully programmable with SCRATCH. This means that a whole load of cool programming and robotic projects will be accessible at KS3 in the next two years.
We think for now just enjoy some of the great things people are doing. We personally believe that the Raspberry Pi should be seen as the STEM extension project for schools rather than as a KS4 resource.
Some of my favorite projects:
Robotics with Raspberry Pi http://www.youtube.com/watch?v=IFH-dxR6Neg
Quadcopters with cameras http://www.youtube.com/watch?v=iSKVnFI_7HA
Collection of some cool projects http://www.youtube.com/watch?v=i1SyIXeFUB0