Panorama tools is a high quality and free panorama stitching software package.
Hugin provides an easy to use graphical user interfaces for Panorama tools.
There is a FreeBSD Port under preparation
Autopano: Automatically identifies control points. Works with Hugin, PTAssembler, PTGUI
Enblend: Overlays images so to make the seam invisible. Works as a plug-in for Hugin, PTAssembler, PTGUI
ImageMagick: Batch process images before using Enblend, e.g. when you have large black areas because of a pitch angle.
Plugins for the Gimp
PT Lens lens distortion correction