After finding the Secret Projects Forum, I began poking around and found the US Space Shuttle Projects thread. I'll leave it up to you to explore as you see fit. There are lots of cool references...too many to try to list here. I will, however, extract some links to the San Diego Air and Space Museum's photo archives. You can find many more by navigating back and forth and you can always look at their entire Space Related photo-set. I have previously referenced the SDASM's Space Shuttle concept photos, but I couldn't resist posting another one.
[I checked a couple of my previous posts and found the embedded photos are broken. The SDASM has once again fiddled with their Flickr sets and broken my links. I have no interest in going back to fix them. If you are interested in Space Shuttle related eye candy, I strongly suggest you look through the photo set noted above. If history holds true, the following links and the embedded photo will also disappear.]