Okay, this really overlaps the stuff above, and it's more-or-less a place-holder now for things I don't want to forget.
- Lin4Astro is a CD-based tool-suite for doing astronomy with a webcam under Linux. The above link will take you to the English-language version of the web site, but the native language is French. I haven't used the above yet, but I hope to get my laptop set up to run Linux and give it a spin.
- David Whysong's Linux tools; David Whysong is (was?) an astrophysics graduate student and he has put together a few Linux-based tools for analyzing images under Linux.