Cheetah 3D (http://www.cheetah3d.com) -- software for modeling, animating and rendering 3D objects -- has been updated to version 5.5. The upgrade adds a particle system.
Now you can create not only fountains and waterfalls but also complex motion graphics and scene from nature, like swaying forests. Since the particle system supports instancing, it is now possible to render extremely complex scenes like jungles or hordes of aliens. Since the new particle system is also scriptable, you can even create your own custom particle systems via an easy-to-learn Javascript API.
Cheetah3D costs US$149 for a single user version; however, version 5.5 is a free update for all registered users of version 5.x and is a $69 for an upgrade from versions 1.x, 2.x, 3.x and 4.x.. It requires requires at least Mac OS X 10.4 and 16MB of VRAM. It's a Universal Binary product, which means it will run natively on both PowerPC and Intel Macs.