I recently revisited AutoStitch and tried the Windows demo application that was released last year. The results were completely amazing and it's the most easy-to-use, powerful panorama maker I've ever used on any platform. Why this isn't built into Photoshop, iPhoto, Picasa, Flickr, or cameras yet is beyond me:

The most complex photo stitching problem ever, and the mystery and story of the Unicorn Tapestries: