Creator of Age of Empires Online Robot Entertainment have readied their PC demo for Orcs Must Die, which you can grab at the source.
Never heard of it? It's a tower defense game with a cartoonish look and accessibility in mind. We'll have screens and impressions up shortly.
Orcs Must Die launches October 5 on Xbox LIVE, at which point a demo will be available there, too. The PC version launches October 12 for some mysterious reason.