Maybe a little OT but you may want to check out Computer Graphics: Prinical and Practice by Foley & vanDam (and others). There was quite a bit dealing with particle systems. New versions of the book have actual C code. The older ones just had math notation. (I found it very hard to fathom due to my lack of formal mathematics education.) I bought mine years ago and it was fairly expensive (~$70 USD.)

-Lee

"To be civilized is to deny one's nature."