Actually, Noveroth, I've found that the easiest explosions that still look great are generated on the fly. I like to use a simple bright white circle for the center of the explosion, and then spew out more circles in all directions, animating the smaller circles to fade to yellow, red, and then a smoky haze. Throw in a bit of shrapnel if you want it to look even better. Also, sound effects are absolutely vital to make it really seem like it exploded.