Panoramic Image Stitching Tools for Unix?

jbuberel asks: "I just got myself a fancy new Canon Powershot S400 camera. One of it's nifty features is it's 'Panoramic Assist' mode that helps you line up a series of images that can later be stitched together to form one larger panoramic image. Of course the software that ships with the camera to do the stitching is Windows-only. After spending some time probing freshmeat.net and google.com, I came across one dead project, and another relatively academic project who's tools are largely undocumented. So are there any up-to-date tools for composing panoramic photos in Unix? With so many digital photo afficianados out there, I was surprised there wasn't an easy-to-use GIMP plugin for this."