Flint
Actionscript 3 Particle Engine for Flash and Flex
...This first tutorial will introduce the basics of Flint through a project to create a snow effect. Our effect will be snow flakes drifting down the screen. Each snow flake will be a particle in our particle system. If you want to see the final effect, scroll to the bottom of the page. This tutorial works with version 4.0.0 of the Flint library. This example creates a 2D particle effect. For 3D particle effects the principles are the same but you use a 3D emitter and 3D behaviours. First create a new Flash file (Actionscript 3). Set the stage size to 500 pixels wide and 400 pixels high, set the frame rate to 30 fps and set the background color to black.