Excellent summary of the combine and all of it's events
http://www.sportznutz.com/nfl/draft/combine.htm
Here is a video that shows many of the tests
http://www.youtube.com/watch?v=iGYSyNcd6FY
Here is an agent explaining what the players face.
http://video.google.com/videoplay?docid=4182404264375166000&q=nfl+combine&total=143&start=0&num=20&so=1&type=search&plindex=13
There's a lot of good content here Rich. I'm sure more to follow.
http://www.nfl.com/combine?campaign=gsi_g