CS 3.0 Skinning: Chameleon Introduction
Most of the other Telligent bloggers have already mentioned it, though I thought I'd throw in my mention. Ben has started posting a series on skinning in Chameleon, the codename for the theme system in Community Server 3.0. Definitely check it out. Ben has put a lot of work into the skinning in CS 3.0 and it is truly amazing. In my opinion, it is the best combination of the two goals of theming, that often times at different ends of the spectrum: skinning made easy so anyone can do it, skinning that is powerful so you can do a wide variety of customizations. Chameleon accomplishes both.
Ben starts off the series talking about how Chameleon is differen than CS 2.1, namely addressing some of the problems with skinning in 2.1 and how they are solved in 3.0. He then breaks into a series about the base classes in Chameleon, starting with single value controls for things like "I want the author's name placed right here", and then he'll be posting on list controls, conditional controls (so you can accomplish what I was talking about here), and many more.