Now just so that you are not confused about the potentials of the Raspberry Pi as a robotic processor/controller, it has great potential for small computation and can run Linux and all the great features that come along with it. But this is a Arm processor and not a typical PC cpu so it is limited by its architecture and power capabilities. Some portions of Linux code have not been completely ported to ARM processors so you will be limited at the moment to what programs you can install. But for most of ROS and the programs I am going to cover in this tutorial, Pi is functional and can be useful depending on the demands of your project. But if you are planning to do any 3d/2d mapping/navigation with a Kinect/laser scanner at the moment I am not sure its possible utilizing just the Raspberry Pi but with time who knows. In the future I will also include another tutorial that connects the Raspberry Pi to a small robot to act as controller. So lets begin..
Step 1: Parts list
Micro USB power supply
USB keyboard and mouse
Monitor with HDMI input
SD Card with at least 8GB (Check this list of compatible cards )
And a computer with either Windows or Linux installed