Habari is an open source PHP / MySQL blogging platform (like WordPress).
MadKast is a blog sharing tool that allows users to share your blog posts via email, IM, sms, etc. It also adds sharing analytics by recording what people do with your posts. They are a TechStars funded business.
1TB of data for $39 (limited offer at 18 Mar 2011). Hat tip Anthony Feint. Plugins for drupal, wordpress, etc. Data is around 10c/gb up to 50TBs, comparable to EC2.
A site about how to get more from your blog, drive revenue, etc.
Open source photoblog software. Funky, clean, described as extensible. PHP / MySQL based.
Weblogs Inc is a blog network of professional bloggers. One of the biggest in the business. Similar to b5media.