Just browsing the Ludum Dare october challenges' page and I came across a post of beauty:

http://www.ludumdare.com/compo/2011/...sum-partikels/ (for the original post)

and

http://sol.gfxile.net/thingamagic/ (for the download page)

I know its written in C/C++ but having played with it and looked at the file format it saves into this is b-e-a-u-t-i-f-u-l to look at. Definitely recommend looking at for anyone into particle effects.