Ehrman has several lecture series available on CD. I listened to his 'The New Testament' and really learned a lot. Highly recommended.

http://www.teach12.com/ttcx/coursedesclong2.aspx?cid=656

He goes into a lot of detail on competing interpretations of the New Testament and the struggles in the first centuries A.D. to define what Christianity would be. Certainly the teachings of Christ were amplified and distorted in many ways.

Right now I'm reading Islam - A Short History by Karen Armstrong and the historical parallels of Christian and Islamic development are striking. In order for both religions to be transformed from very local movements into world religions, they had to adapt to extremely foreign conditions so the problems faced in both cases were similar.

Both movements considered the same sorts of alternatives as far as beliefs and practices are concerned and chose pretty similar paths. Or rather, the paths that have survived and thrived turn out to be similar. In both cases, it's pretty clear that the founders wouldn't be at home in their respective religions' current dominant sects.