I don't know exactly why this sort of thing fascinates me, but Baseball Prospectus has a great article detailing the Tommy John procedure. They also link to Kris Benson's web site, complete with pictures of his arm. And it's free, for all you fellow (meaning: I am one, too) cheapskates. Perhaps its because so many arms in the organization have gone down to injury, or because we hear a lot of talk about pitcher's injuries but not much actual information.
The one thing that the article doesn't go into much detail about--and that it says is a very important aspect--is the rehab process. I've gone through an elbow injury myself, complete with a rehab process, and though I didn't have surgery, I can testify that therapy on elbows can be both very helpful and painful.