I didnt see this posted, so I thought I would share...
I was searching the forums for 2007 bike info and found a URL for 2007 trek bikes in the road forum. Basically I changed around the URL from road to mountain and put in the model numbers for mountain bikes. I have found so far 820, 3700, 3900, 4300, 4300disc, 4500, 6000, 6500, 6700, 8000, and 8500.
http://www3.trekbikes.com/Bikes/2007/mountain/3700.html Didnt try any FS bikes or other models yet.
Nothing really big changed, just some colors, some fork differences and a new model I found was the 6000, looks like a nice bike, has Avid BB5's on it. The 4500 and 6000 come with Rock Shox Dart fork. New model name again I guess.