Processing is also the development environment for the Arduino ( http://www.arduino.cc/ ), a very cool open source hardware platform for small-scale electronics projects/prototypes.
I use both of these pretty heavily at work and at home and they've proved to be immensely useful for whenever I want to test out ideas that pop up in my head from time to time.
If you're on a Mac, there's also NodeBox ( http://nodebox.net/code/index.php/Home ) which lets you use Python.