Note: Your best experiences for the links below will be in Chrome or Safari. You can get some of this working in Firefox, but as Chris Ziegler just remarked, "It's mega slow."
- These will absolutely blow your mind. Mr.doob's Chrome experiments -- Ball Pool and Google Gravity.
- Here's a roundup of experiments from Ben Joffe, including a rudimentary 3D shooter, a 3D functions plotter, and an HTML5 color picker.
- Some of my personal favorites, KesieV's Akihabara game room. The Legend of Sadness is where it's at.
- Exploding, real-time video.
- WPilot -- a multiplayer shooter. Like Asteroids meets Quake.
- A giant, color-cycling canvas. Weirdly addictive to play with.
- 3D molecules. 'Nuff said.
- Mega Man intro. In HTML5.