Scrum is a pretty straightforward Agile method that can be easily implemented (with some discipline) and which shows quick results.
Read a bit about it here: http://www.controlchaos.com/about
A very interesting read about how implementation of Scrum on a dismal project rejuvinated it can be read in this PDF. It is an excerpt from a book by Ken and Mike.
Here's a diagram that shows Scrum's basic idea: