This sophisticated piece of command-line/Java software is capable not only of panorama stitching but also correcting chromatic aberration (). Best of all, it is free.
Its original author is no longer developing the software, but that has not stopped development of both the original software and also graphical user interfaces. It can be `plugged in' to Photoshop and GIMP (Windows only, not Linux!?).
Panotools mirror site
PTGui -- commercial graphical user interface for PanoTools (Windows only)
Correcting Distortion and Color Fringing (J. Brian Caldwell) -- how to use PanoTools to reduce chromatic aberration (Mr. Caldwell uses PanoTools as a Photoshop plugin)
And for Linux users...
`Missing' sys_ansi.h -- if you really want to compile PanoTools by yourself. However, pre-compiled RPMs are also available.
hugin -- (beta software as of March 2004) A free GUI to PanoTools, for both Linux and Windows. As of March 2004, hugin requires a version of wxGTK which supports XML. That version of wxGTK is not provided with SuSE Linux 8.2 (released early 2003). Users of RedHat/Fedora can rejoice, however, as they have pre-compiled RPMs of wxGTK-xrc available. SuSE Linux 9.1 can use RPMs designed for (Redhat)/Fedora Core 2.