Learn to monitor and control your home & environment with self contained, inter-communicating microprocessors. Arduino / Raspberry Pi Applications include ham radio, robotics, weather stations, model railroading, toys and more. - KK4HFJ
Need a good 12v / 5v / 3.3v power supply for projects? A 400 watt supply can provide about 23 amps at 12.5 vdc or so. If you have an old computer supply laying around, you may be all set. New ones are about $18 (http://goo.gl/ilrXyi). Mike McRoberts has a great instructional on the conversion process.
His blog has lots of great projects, and we really recommend his Arduino book: Beginning Arduino