I spent most of a weekend getting Wordpress Mu (aka WPMU) up and running this site. It was a mixed experience.
WPMU is a modified version of Wordpress designed for hosting many blogs on a single server. It’s the software which drives the Wordpress.com service.
That’s the blurb, anyhow. As it turns out, Wordpress.com have a bunch of custom code which they haven’t quite shared completely. Such as the nifty code for domain mapping. But that’s neither here nor there.