21Publish: Turnkey solution to start your own branded blogging community. Useful and usable when used in the context of a school/college set of blogs or for custom webhosting/community solutions such as that of a forum or an ISP. Another niche market served.
[EDIT] I must add that after looking at things closely, it looks like a multi-user blogging tool, much like WordPress with a different face. It will take a closer look at the multi-user features to understand if it is different at all.