Note: some of these also describe the use of PyXML, which is an outdated XML package that is no longer maintained and should not be used in new code.
Introduction to different XML libraries: http://diveintopython.org/xml_processing/index.html
Python XML FAQ: http://www.rexx.com/~dkuhlman/pyxmlfaq.html
ElementTree tutorial: http://effbot.org/zone/element.htm
lxml tutorial: http://codespeak.net/lxml/tutorial.html
Python XML Processing with lxml: http://www.nmt.edu/tcc/help/pubs/pylxml