Unconditional Parenting (http://www.amazon.com/Unconditional-Parenting-Moving-Rewards-Punishments/dp/0743487486/ref=sr_1_1?ie=UTF8&s=books&qid=1260936571&sr=8-1) is the book I would recommend. He also has lots of articles on his web page (http://www.alfiekohn.org/articles.htm) that are in the same vein. He writes about both parenting and education (he is a former elementary school teacher), and I use some of his teaching articles in my courses.

Happy reading!