Hack42SA007 has put together a instructable to help you all choose your power source for your projects.
"Every electronic or electric project needs power, but how to select what kind of power supply you project needs. There are so many types out there, what are the things to keep in mind when browsing your local store or digging in a box of recycled parts"?
"In this instructable I hope to give you a clear idea of what the differences and caveats are".
Read more; http://www.instructables.com/id/Powering-your-project/