|Applicable Blender version: 2.63.|
One of Blender's powerful features is its Python API. This allows you to interface with Blender through the Python programming language. The Python interface allows you to control almost all aspects of Blender, for example you can write import or export scripts for meshes and materials of various formats or create procedurally generated textures. You can also create complete animations procedurally and write scripts to modify existing scenes in any way you can think of. On top of all, you can easily create a user interface for your script, transforming it into a generally usable tool.
The relevant section of the Blender User’s Manual is here.
Download Python Scripts from the Blender site here.
This forum on blenderartists.org discusses Python scripting.