I also once did search for something like this but apart from some very bad programs which "simulate" a couple of moving low res sprites and save that into a bitmap for each frame there wasn't anything worth mentioning. So you either look for free explosion animations (very hard to find too but there ARE a few ones worth using) or you look for someone with a decent 3D package (e.g. Lightwave, Maya and so on) with some knowledge & skill who could make something like this there...

There also are some commercial packages for movies you can buy but they are rather expensive...

Enjoy your meal
Toast