Michael Meier of Oakado blog (fun illustrations, btw) found this awesome interactive installation called Bright Nights in New York City's Union Square:
The project was called »Bright nights« and the code for the installation was made with java and c++. It workes basically like the particle-system in maya or 3d studio max but with an essential difference, it is generated in real time. Overall Marcus and Andrew did 12 different interactive games for this project which had the ability to morph into each other. So long-lasting fun was guaranteed.