Keith recently posted the finalists for his 25 Lines of Code contest.
I just briefly clicked through the swfs... there are some amazing projects there. You have your classic fractal tree, and classic partical fireworks (both done extremely well). Then you have a few full fledged games... which I wouldn't think would be possible in that short amount of code. A few nice 3D objects... I definitely like the interaction with the dandelion, altho the cube with the Conway's Game of Life is no slouch either. There is a very cool flocking example and then a few organic math based objects... including one that reminds me of the root in Pan's Labyrinth (I just watched it last night so its on the mind). All in all, I am extremely impressed.
Now I am looking forward to being able crack open the FLA's and see what kind of Black Magic they used to accomplish these pieces. Should be able to find some new tricks and techniques crammed in there.