The programming language is free, and so the tutorials or book references listed here are free... :D
General
- Tutorial by Guido van Rossum(the creator of python)
- Byte of Python
- How to Think Like Computer Scientist: Learning with Python
- Introduction to Computer Science and Programming by OCW MIT
- A Gentle Introduction to Programming Using Python by OCW MIT
- Python Classes and Technology Lectures by Google Code at http://code.google.com/edu/languages/
- Python in wikibooks http://en.wikibooks.org/wiki/Python especially these http://en.wikibooks.org/wiki/Non-Programmer's_Tutorial_for_Python_2.6 , http://en.wikibooks.org/wiki/Python_Programming
Scientific/Engineering
- PythonScientific that used for tutorial in past scipy and euroscipy conference
- Video tutorial for scientific and large-scale computing at ShowMeDo by unpingco
- Training material from Ohio Supercomputing, Python Programming for High Performance Computing
