Hugin because penguins love you :-)

[Abarbarian]

"Anybody who has tried to join together two or more independent images in those tools will have discovered, however, that certain manipulations fall into a class of their own. For that kind of work, hugin would appear to be the only choice. Your editor has long intended to play with hugin; the threat of having some real work to do finally provided the necessary motivation."

http://lwn.net/Articles/351053/

Enjoy.