When I'm bored, I like to toy around with some practical simulators. If someone could provide the links to some nice fully-functional simulators of sorts that would be entertaining for me, that would be nice.

Right now I have a star system simulator... its just circles with masses and velocities.... it simulates gravity nice and you can make some neat systems.

I also have a traffic simulator ( Traffic Sim 5 with Synchro 5 ) which is a fancy program to.... well, simulate traffic patterns. Very customizable and I enjoy toying with it.

If anyone has anything else thats interesting, please link it to me.