Phun - a 2D physics sandbox
Thanks to Clarence Fisher's Twitter message, I've been introduced to Phun, a 2-D physics modelling application. Still in Beta form, this freely downloadable application has been created by Swedish computer science student Emil Ernerfeldt for his Master of Science Thesis.
Currently available for Windows and Linux (with a Mac version in development), Phun is intended to be a playground where people can be creative. It can also be used as an educational tool to learn about physics concepts such as restitution and friction.