http://www.thewayoftheninja.org/n.html

Everybody should give this game a go. The game is simplicity itself. Three buttons: "left", "right" and "jump".

It's a platformer with speed as the goal. Check it out.

(if this has already been mentioned, my apologies)

Edit: (funny walk-through of a level)

http://youtube.com/watch?v=h5XNNqRyYd0