I'm currently -- and somewhat unhappily -- using MovableType. My usage isn't totally normal.
Basically, I have one MT directory. There are currently ten users, each with their own blog. The main page, however, runs a plugin I found for MT that will pull in posts from all ten of the blogs.
I'm really impressed with WP. But is there a way to do this? It's important that it work both ways: it's ten separate blogs (domain.com/username), but also one collective blog (domain.com).
Surprisingly, this doesn't seem to be an entirely common use of blogs. But does WP support this? Is there a plug-in to do it?