Best or most reliable resources for understanding and training dogs?

What are some of the most insightful, reliable resources (books, DVD, famous dog trainers) for understanding and training dogs?

I have heard of celebrity trainers such as Cesar Millan, Kevin Behan, Ken Ramirez, or techniques such as positive reinforcement, the alpha theory, etc. Clearly not all dog trainers agree with one another, with makes it more confusing; I’d be watching the Dog Whisperer for a time then someone would tell me that Cesar’s method is outdated.

I’m lucky that my only dog, a Lab, is very intelligent and thriving even without formal dog schooling, but I would really benefit from extra reading on dog training/psychology. Thank you in advance for any help!