Bethesda marks the 20th Anniversary of Wolfenstein 3D -- the pioneer 3D first person shooter -- by releasing a free-to-play browser version of the game. Blow some Nazis away with the director's commentary from John Carmack running in the background, or go old-school and drench the walls in blood and gore. (Unless you live in Germany where the game is illegal.) Via. [more inside]
Flame is a really nice web-based experimental painting programme from Slovak animator and designer Peter Blaskovic.
Flash Java Fun - 'Building Houses With Side Views' Entertaining Java game/exercise/doodad. [more inside]
You have spacial skills. Apply them in Building Houses 2, on mathsnet.net. Or freestyle in Building Houses 1. Or at night! Oh and also there's like a hundred more puzzles over there too. Some java required.
Teddy: A sketching interface for 3D freeform design (in Java). Noodle around with the online applet (see the tutorial for instructions; there's also a demo in .avi format), or download the program so you can save your creations. An even niftier upgrade is available, SmoothTeddy (.avi demo), but SmoothTeddy doesn't have an online version to play with.
J-Track 3D is an interesting JAVA web-app offered by NASA which gives a 3D interactive display of over 500 satellites currently orbiting the Earth.