GeoServer has been mentioned on the website linux.com.  In their Tips And Tricks area, they have written a quick tutorial on installing and running GeoServer in Linux (Ubuntu, specifically), downloading a TIGER shapefile, loading the shapefile in GeoServer, and even a brief introduction to styling.  This page covers a lot of ground in a short space, but I think that’s its beauty in it.  Some might be a little intimidated by the SLD styling code (someday a graphical styler with make raw XML coding unecessary) but it’s currently just a part of the process.  All in all, it’s a great tutorial, and might be a good read even if you’re already familiar with GeoServer.  There’s always more to learn, after all.