b2evolution is probably the most comprehensive blog engine you can find! It includes almost any feature you could expect from a blog tool, and more

boastMachine is an open source, state of the art publishing platform that makes your web publishing experience so fun and easy as never before! From the fully automated installation to advanced content management featuresto spam fighting, boastMachine provides you with all that you would ever need!

Loudblog is a sleek and easy-to-use Content Management System (CMS) for publishing media content on the web. It automatically generates a skinnable website and an RSS-Feed for Podcasting. Just upload your audio/video files, add some notes and links, and you’re done!

BLOG:CMS is the most complete, feature-packed, personal publishing system on the market, developed by Radek Hulán. It includes state-of-the-art weblog, forum, wiki engine, news aggregator (atom / rss), and photo gallery.

Serendipity is a weblog/blog system, implemented with PHP. It is standards compliant, feature rich and open source (BSD License). Serendipity is constantly under active development, with a team of talented developers trying to make the best PHP powered blog on the net.

Nucleus offers you the building blocks you need to create a web presence. Whether you want to create a personal blog, a family page, or an online business site, Nucleus CMS can help you achieve your goals.

blur6ex is a simple weblog and content system built with PHP. It offers basic features found in more established systems and is extensible enough for any number of new features to be added. Ideal, at the moment, for those who don't want overkill in their setup.

WordPress is a state-of-the-art semantic personal publishing platform with a focus on aesthetics, web standards, and usability. What a mouthful. WordPress is both free and priceless at the same time.

A free, flexible, elegant, easy-to-use content management system for all kinds of websites, even weblogs. When it comes to publishing on the internet, beginners and experts alike are met with a bothersome paradox: word processors and graphics applications allow anyone to do a pretty good job of managing text and images on a personal computer, but to make these available to the worldwide web – a seemingly similar environment of documents and destinations – ease of use vanishes behind sudden requirements for multilingual programming skills, proficiency in computer-based graphic design, and, ultimately, the patience of a saint.

bBlog is a powerful, elegant personal publishing system written in PHP and released as free, Open Source software under the GPL. It is a flexible but simple way to blog that works for blogging beginners, and can grow into a more advanced user's needs.