Frank over at VerySpatial.com wants to know where the GIS-oriented Linux distributions are. Well, here are
GIS-Knoppix: A GIS-oriented version of the bootable Knoppix Linux distribution, but can be installed on your computer as well. Has GRASS, OpenJump, qGIS, MapServer, Thuban, and a bunch more.
Host-GIS: A Linux distribution designed around MapServer; comes with example installations and data.
Archeos: An archaeology-oriented Linux distribution, but with lots of GIS applications as well (GRASS, MapServer, OpenJump, SAGA, etc.). But good luck downloading a copy of this – not only is it over 1 GB in size (a DVD ISO file), but if my browser doesn’t crash when I try to download it, I get a 404 error page.\
Arch Linux (AEGIS): Mentioned in the comments; GRASS, JUMP, qGIS, MapServer and a bunch more.
I install a copy of Linux on my computer every few years, then take it off – doesn’t offer enough value for the time it takes to install, configure and learn it. I may give Wubi a try, since it seems to simplify the installation process for Ubuntu in Windows, and I’m waiting to see what happens with LINA, a project to make Linux software runnable on Windows and Macintosh with a native OS look-and-feel.