Boris FX offer a free, standalone version of Particle Illusion, which is the product I'm reviewing here. There is a pay-for upgrade, but you don't need that to get some pretty impressive results. I'm not affliated with Boris FX in any way. I made this video to shout about PI as I think it's pretty cool and I've made it my mission to share information about any free resources I find. I think for those of us on a budget, Particle Illusion Standalone is a great free alternative to expensive plugins like Trapcode Particular and Superluminal Stardust.
After explaining a bit about the software, I then show how to use it for a really simple requirement... rendering out an explosion which I then bring into After Effects.