http://dan-ball.jp/en/javagame/dust/

At first it seems like your basic particle-properties thing, where you've got water, fire, oil, sand... etc.. But this one has a whole bunch more stuff than the usual, and also includes wind motion which affects everything else in brilliant ways. For example, scatter some sand about, and ignite some nitro on top, and you can see the shockwave hurtle up to the top of the box, and round and back down... so it's not just the initial explosive blast, but a rippling effect.

Very cool!

Incidentally, the wind motion might remind you somewhat of the fluid dynamics seen in the outstandingly inimitable Plasma Pong, which seems to have been squashed by Atari corporate evilness. (Seriously Atari dudes... I think you *might* have a fair amount of mileage from Pong already... give it up!)