Mark's Daily Apple is one of the best sources for Paleo/Primal living that I have encountered to date. He's not a radical my-way-or-the-highway kind of guy and I respect him enormously. His book, The Primal Blueprint, set me up for a lifetime of success.
Michael R. Eades, M.D.
William Davis, M.D. author of Wheat Belly
Dr. Jack Kruse, neurosurgeon, blogger, and author of Epi-paleo Rx