b2evolution is an open source blog system. b2evolution forked from the b2/cafelog project in 2003.
From the Author
b2evolution is a news/weblog tool. You enter your news items through an easy-to-use web interface and the updates will appear dynamically on your webpage. The script also handles archving and commenting. b2evolution is an extension of the 'b2' blog script.
Author website: http://b2evolution.com/