Processing (http://processing.org) is a Java-based graphical programming language. Great for getting instant feedback and making pretty pictures.
The IDE is the same one that the Arduino project uses. Not a lot of features, but it’s quick and works well.
I wrote a simple particle gravity app, and it animates really smoothly. I’m looking forward to using it to make more eye candy!
App is attached as “planets.txt”, rename to “planets.pde” for the Processing IDE to pick it up.