Autumn Leaves automatically creates an optimized setup to simulate dozens of flying / falling tree leaves, with proper collisions, deformations, dynamics and aerodynamics. You only need to have high-res and low-res models of your leaves (you can combine several different models), and a NURBS surface to place the leaves on. After applying the script, you cand add more stuff to the simulation, like fields, or collisions with animated objects and characters.
You can see this very simple example video (http://vimeo.com/7716060) .
This script is an evolution of a technique I developed to do leaves simulations in the film Planet 51 (which, by coincidence, comes out in US cinemas today!). It creates a relatively fast low-res single nCloth simulation, and transfers its animation to the high-res leaves through the use of wrap deformers.
I have many ideas of how to take this tool further, and make it more powerful / flexible. So if you use it and have any ideas for improvements, let me know. Same thing, of course, if you find any bugs (they are always there, creeping about somewhere...).
You can find more info at my blog (http://www.deviantart.com/users/outgoing?http://www.mayec.eu/blog.html).