Microsoft Image Composite Editor (or ICE) is a multiple image assembler that allows you to quickly import images to generate panoramic photos. You just simply have to drag and drop photos into the application, and ICE will automatically scan and combine the images to create a seamless, high-res panorama.
Despite its long, complicated name, Microsoft Research's app is simple and straightforward. You aren't required to prepare photos or perform any complex ordering. ICE automatically scans each image to determine the best method of stitching images together, both vertically and horizontally. Although I didn't expect it to perform any photographic miracles, I was indeed impressed with how fast it performed and how well it preserved the final quality of the resulting image. Photographers who want to document the world and share their grand vision will come to appreciate its robustness, as ICE supports hundreds of photos together in a single process. Knowing its capabilities, ICE did give me peace of mind the next time I went to take a large panoramic photo.
Other goodies include direct sharing with friends in 3D via Photosynth, Microsoft's wraparound photo-publishing platform. What makes this impressive is that you can create Street View-like images and 360-degree "photo tours."
Microsoft Research's ICE is available for the stellar price of free, but it doesn't offer official support.