Blender is a open-source program for 3-dimensional modeling and animation, and socalled rendering. That means you will get near photo realistic images of the models you create. Blender is just as advanced as for instance Maya og 3D Studio Max, but this allso means that you'll need to spend a lot of time learning to use the software. You can find information and tutorials on the Blender official home page. You will probably also want to have a look at the official wiki-page.
With Blender you can model particle-effects, you can simulate wind, hair, liquids and much, much more. You can also make your own games directli in Blender, and Blender is capable of complex collision detection.