Tweaking the particle engine

I've been wondering how to make good looking particle explosions for some time now. Seems that no matter what kind of image or parameters I used, the explosions always ended up looking like separate particles. Like this example image:



Today I finally figured that doing a double rendering pass on the particle layer using different glBlendFuncs, I can blend the particles together and achieve a much better result:



I'm also looking into recursive particle emitters (emit particles that emit particles that emit particles...).