Microsoft has a free program called 'Image Composite Editor' (or ICE)
The most 'exciting' thing about ICE is that if you have a video of a panorama (so easier and quicker to do than several photos) it will convert that to a single panorama image.
ICE works well and has a very good blending engine - well worth the download (2.17 M Here's a review of ice from 2119 by Gizmo--best free digital image stitcher link: http://tinyurl.com/3zcwlye ICE also may be Dld from: http://research.microsoft.com/en-us/um/redmond/groups/ivm/ICE/
An application that takes several single images and combines them into a larger image.
Some time needed to learn how to use all it's features, but not massively complex to learn.
If you have a stable hand, you can even use this application without a tripod.