This is the start of a Blender/Python manual. At the moment the most useful areas are the optimization guide and the cookbook.
Python is high-level, easy to learn scripting language, that can be applied to various aspects of Blender, and MANY other things. For an introduction, download it. Then google Python Tutorial, and you'll find a wealth of excellent beginner's tutorials. Once you've mastered the basics, you can start learning Blender type stuff.
Please feel free to add content to other areas.
- Blender Python 2.46 API Reference — Python API Reference. Keep this under your pillow.