DALiWorld (www.daliworld.net) is a distributed virtual aquarium by DALi, Inc. It touts itself as being an Artificial Life simulator, which is a bit fanciful, but it is a cool program in its own right. Coded in Java and graphicked in Java 3D, the aquarium is pretty much platform agnostic. It can also be used as screensaver.

Intermittently, fish will arrive and depart from your patch of the ocean from other users' aquariums. By right-clicking on them, you can see where each fish has been in the (real) world. Leave it on for a while and you get a teeming array of sealife (a wide range of fish species are authentically modelled, apparently). The animation is pretty fab too.

Although the controls are a bit unwieldy and there are some graphical glitches (to be expected, especially as the software is still beta), this is a fairly good example of what is possible in distributed applications, and what Java is now capable of. I can't wait to see some more game-oriented projects build on this technology.