I have downloaded a few demos this weekend of some pretty great games for the PC and thought we should have a thread for stuff like this. Demos are actually a great way to tell if a game is any good or not because most of them give you at least half an hour or so to check out the various features and get a real feel for what the gameplay is like.
Also, feel free to post any information on stuff for the 360 or PS3. There are lots of game demos up on both networks. I believe both Trine and Braid are available on both consoles and probably have demos in the marketplace.
Trine - $19.99 ... this is just incredible. I may actually have to buy this game. I don't think I've ever seen a 2D platformer that looks this good.
World of Goo - $19.99 ... Interesting puzzle game where you build goo-based structures in an attempt to reach a goal. The later stages of the demo are really tough.
Braid - $9.99 ... for $10, it's kind of hard to avoid the full version of this game. I played it for 10 minutes and was amazed. Another addictive 2D platformer.