FireFox v1.5 has implemented a new feature called Scalable Vector Graphics (SVG) which is a language for describing two-dimensional graphics and graphical applications in XML. Basically you can create cool graphics stuff with very simple XML code. Unfortunately it’s not a very widely supported technology, so you’ll need FireFox v1.5 to use it.
People have already created a couple of fun things using this new technology:
Try to get the moon into orbit
Walk around a world that looks like a simplistic Doom / Wolfenstein level