The current stable release of Blender is 2.49a

On-line documentation for Blender's Python API is here:
http://www.blender.org/documentation/249PythonDoc/

The current development version of Blender is 2.55.
This version has a new Python API. Documentation and an introduction to the new API are here:
http://www.blender.org/documentation/250PythonDoc/