> A few years ago, I played around with a package called 'Struck' by Gerald
de
> Jong, who introduced me to it over some geek dinner. I can chat very long
> about it, but just go to http://www.beautifulcode.nl/struck with a
> Java-enabled browser and have some fun

As you mention fun and Java applets:

sodaconstructor
http://www.sodaplay.com/

It is only 2D but the creatures are living!

Andreas