All I can say is Wow! Autostitch is a program that some programmers developed at the University of British Columbia. You can feed it a whole batch of assorted pictures from a single collection and it turns around and sorts them all out like a jigsaw puzzle, seams them together magically and then manages to blend them into one single amazing image. It's incredibly easy to use but quite sophisticated in its ability to assemble images accurately. Check out the samples and demo on their site.
This composite is from six different shots I took over Lake Union across the street from my studio. Needless to say, you can tell I'm humbled and impressed by these guys! IMHO this program is better than ANYTHING Adobe Photoshop offers and the Beta version is still available as a FREE download right now.