Head on over to the blender nation blog and have a look at some of the things it can do.
You are going to need some patience to master Blender. It takes a while to get the hang of editing three dimensional objects and the user interface is very rich. Blender is feature filled and has a nice professional finish to it. The software is very powerful. If you want to render a movie like Elephant's Dream, the software allows for using a render farm.
Blender imports VRML 1.0, DXF (Autocad), Videoscape, STL, 3D Studio, AC3d, Collada, DEC objectfile, directX, Google Earth, Lightwave, Quake, Nendo, OpenFlight, ProEngineer, Radiosity, RawFaces, Stanford PLY, TrueSpace and Wavefront files.
Not everything has to be free. There are plentiful resources of pre-made objects available for sale that are royalty-free and that can save a ton of time. If you're interested in these, try out turbosquid.com. They have thousands available.
Modelling programs use descriptions of shapes called meshes to form the basis of objects that you can manipulate. You can find some meshes, and other things for free here:
- NASA Space Educator
- JPL Solar System Simulator
- Trek Meshes from Star Trek
- Google it
- Ocnus Rope Company Models
- Level of Detail
The meshes only provide a framework for the objects. There are also materials, textures and finishes that are used to render your artwork into something hopefully photo-realistic.