In 3.0, "the merge" happened between what was WordPress MU and regular WordPress. Now you can have multiple sites in one installation called a Network. Users will learn how to create a network, get it up and running smoothly, and all the little hints and tricks you'll need to know to run one successfully. We'll also cover how to give each site it's own full domain. No more running a half a dozen separate installs on one server!
Bio: Andrea Rennick discovered WordPress MU by accident. Since then, she has written extensive tutorials to help others, developed a couple themes and plugins, contributed to WP 3.0 help text, and acts as a moderator on the official support forums. This year, she is also co-authoring the WordPress All-In-One Desk Reference with Lisa Sabin-Wilson and others.