Autostitch was the one that worked quickest and easiest for me
I use Autostich (http://cvlab.epfl.ch/~brown/autostitch/autostitch.html)and Microsoft Image Composite Editor (http://research.microsoft.com/en-us/um/redmond/groups/IVM/ICE/)
If you have a Canon digital camera it might have come with a program called PhotoStitch. Maybe other cameras come with similar software; worth checking.