Here's my favorite so far:

http://demoseen.com/langton.html#*/*/*/*/*/*/*/*/*/*/....

[EDIT: and its cousin: http://demoseen.com/langton.html#*/*/*/*/*/*/*/*/*/*/....+-+... ]

Edit: Just made a small change that will make things look prettier, though. If you have the command string XYZW, the command string XYZWXYZW is 100% equivalent, except for the shading (due to the cell values looping around). So when you put in a command string, it's automagickly extended to > 64 bytes now, guaranteeing smooth shading.

Btw, just implemented yet another new feature: the '@' command is an ant bomb. If there are multiple ants in play, @ kills the one that triggers it. That lets you fork without completely annihilating your system.

Edit: Really don't like the color stuff. I've left in $ and ^, but I've turned it off for forks. It just looks like random nonsense, sadly.