Free Advanced Photo Stitching Tool
The Image Composite Editor allows you to perform advanced photo stitching, and the cost is right: free.
Microsoft Image Composite Editor works on 32-bit and 64-bit versions of Windows XP, Windows Vista, and Windows 7. There is no upper limit on the image size.
To find out more about this interesting free product go to:
https://research.microsoft.com/en-us/um/redmond/groups/ivm/ICE/
You will also likely want to take a look at HDView:
https://research.microsoft.com/en-us/um/redmond/groups/ivm/HDView/
To find out more about the concepts and strategy behind the Image Composite Editor, you might want to read the article at:
https://research.microsoft.com/en-us/news/features/siggraph2010-072610.aspx