Books available from effbot.org.
The books are copyrighted, but are free for personal use.
Python Standard Library
Based in part on over 3,000 newsgroup articles written by Python veteran Fredrik Lundh since 1995, this book provides brief descriptions and sample scripts for all standard modules in the Python 2.0 library.
The O’Reilly edition: Python Standard Library.
The effbot.org edition: (the eff-bot guide to the) Standard Python Library.
An Introduction to Tkinter
The pythonware.com edition: An introduction to Tkinter
Python Imaging Library Handbook
The pythonware.com edition: Python Imaging Library Handbook.