I'm sure that most of you have seen it before but for those who haven't: www.archive.org This one site that I digg very much. It includes the history of internet.. just type in an URL and it returns a few versions of that site from the past. You can look up pretty much whatever you want that's been spidered. Here's how DP:s forum looked like in 1,5 years ago, (http://)web.archive.org/web/20040329201635/http://forums.digitalpoint.com/
Unfortunately, they seem to have stopped storing sites. I haven't see any recent data available for a long time now.