At E3 07 during Ubisoft's Press conference, Jade Rayed showed an extended demo of the Assassin's Creed. The new demo takes place in a "historically accurate recreation" of Jerusalem. It looks really impressive and shows some of the nice features that the game will have.
This is one of the most anticipated games this year, and it sure got a lot of attention at E3. The game is scheduled for a November release.
You can check out the on stage demo here. Previews can be found on Gamespot and ShackNews.