Windows software
[PanoTools] is a high quality and free panorama stitching software package.
Both [PTGui] and [PTAssembler] provide easy to use installers for panotools.
stitching software
I use PT GUI.
A free and opensource GUI for Panotools is Hugin.
See the Panorama Tools project at sourceforge for more Panorama Tools related software.
Anything else?
photoshop plug-ins
There are some in the original distribution by Helmut Dersch
viewers
can somebody please link to Fulvio's viewer and other tools?
PTLens
Thomas, how do we fit your wonderful tools in this space? they are not directly used to create panoramas but they are sure part of the family!