This was a hosted blogging platform that I developed. The site hosted 1,200 blogs. The first version had blogs, blog posts, blog comments, tagging, blogrolls, user profiles, RSS feeds and a theme system. The second version added multiple blogs per user, multiple users per blog, AJAX blog settings, AJAX private messages, AJAX tagging, favorites, voting, nested blog comments and a friends list.
It was built with LAMP and jQuery. I think I spent about 5,000 hours developing this project between 2004 and 2008. The site is no longer live but you can check it out on the Wayback Machine.