When I pay attention to the people listed below I feel better, perform better, and live better. Robb Wolf alone gives you all the information needed to lose that belly, feel great, and be healthy, but I found the others very helpful, too.
Dan John makes it fun and easy to stick with it; Steve Maxwell and Pavel Tsatsouline help you work out anywhere, gym or no gym; Krista Scott-Dixon debunks myths so you can talk to your friends about what you're doing; and the others fill in the gaps nicely.
Krista Scott Dixon provided the intellectual framework and technical details I needed, as a geek, to get started with weight training in the late nineties. She also loves busting the myths that keep most people from exercising effectively.
Mark Rippetoe is a great source for details about the how and why of strength training.
Dan John has inspired me, saving me from boredom and lack of motivation.
I think it was Dan John who first introduced me to Tabata, the amazingly effective four-minute workout.
Steve Maxwell and Pavel Tsatsuline both have videos that helped me learn to encourage my joints to recover quickly and naturally from the occasional aches and pains of training. They also have great things to say about exercise.
Both of these guys are
Valery Fedorenko helped me understand kettlebell exercise at a deep level.
Arthur Dreschler made a video and book with enough technical depth for me to learn to do the olympic lifts. The clean and jerk is my favorite exercise.
Robb Wolf helped me to question my habits and really think about their combined effects on my health---sleep, hydration, nutrition, and exercise. I went from over a decade of "scary" levels in triglycerides and bad cholesterol to well within "normal" levels after about six weeks of trying to do things Robb's way.
John Brookfield helped me to improve my hand strength, eliminating a weak link that was holding me back.