Mephisto: http://mephistoblog.com/
Typo (site seems down)
Best regards
Peter De Berdt
simple log would probably be a better starting point. Mephisto is less of a blog engine and more of a publishing platform.
You might also look at Beast. It's a forum, but its very light (500 LOC) and written w/ most of the latest rails stuff. Forums and weblogs are about the same anyway.
http://beast.caboo.se http://svn.techno-weenie.net/projects/beast/trunk/ http://beast.caboo.se/forums/1/topics/446
