Don't Shoot the Dog by Karen Pryor
This is the "Bible" on positive reinforcement training, or operant conditioning, and how it works - with people, and of course with animals.
Clicking with Your Rabbit
Filled with wonderful tricks and useful behaviors you can teach your bunny, and all the steps you need to teach them.
Animal Training by Ken Ramirez
600 pages of the best papers, articles, and presentations on the topic of reinforcement-based training.