I was just at Noels Tutorial @ windy city rails. Which was good. i bought this to practice what I learned while I was fresh. I must say that I really am enjoying it so far. it does a good job describing the thought process behind TDD, at each stage. All the code samples are working perfectly so far (Only on chapter 2).
This is the best resource I’ve seen to get started if you have very little testing experience. I personally like that it starts using Test::Unit. Because it just works, and is part of the default stack.