Amusing Physics Programs

Below the fold, you can find a list of programs that let you see physics in action. Want to build a Rube Goldberg machine but don't want to have to clean up the mess? Try Phun. Want to try your hand at building a more interesting solar system? Universe Sandbox is for you. Want closed form solutions to Schrodinger's equation for arbitrary Hamiltonians? Yeah, I wish I had a program to do that too.

Phun allows you to construct systems using classical physics with springs, motors, liquid, surface friction, etc. I admit my description seems bland, but it is worth downloading and trying at least once. I like playing with fluids.
Phun is available for Windows, Linux, and Mac OS X.

Universe Sandbox
Astronomy gives us a view of the universe that reveals the fallacy of our petty squabbles, and in the Universe Sandbox, you can see this grander view...and then see what happens if you change it.
Sadly, Universe Sandbox is only available for Windows and requires the .NET 2.0 framework.