Hugin is a panorama stitching and more. A powerful software package for creation and processing of panoramic images. Similar to the windows programs PTGui and PTAssembler. If you want to see some example pictures created with hugin, take a look at thousands of hugin pictures on flickr
The last release of Hugin is available for any platform: Windows, Mac OSX and Linux also there have been many many bug-fixes, improvements to the interface and lots of new features. You can Download Hugin from sourceforge.