Tunnel - a game in javascript and css using jquery.

This is pretty well done, although it's not really too much more than a "proof of concept".

I'd really like to see a lot more movement in this direction from online game developers, and it seems like we're just starting to hit the point where this is really feasible, so I guess we probably will.

No flash, no java applets. No more dealing with crappy or just unstable implementations of plugins on different platforms and browsers(just dealing with differing implementations of javascript and css on different browsers, which is also a bit of a pain, but it's getting better a lot faster.)

Edit: I just noticed this is from a year ago, and there has been quite a bit of game development using javascript. Good.