<p>I've recently started with Python, and am enjoying the "batteries included" design. I'e already found out I can import time, math, re, urllib, but don't know how to know that something is builtin rather than writing it from scratch.</p>

<p>What's included, and where can I get other good quality libraries from?</p>

The Python Global Module Index (
http://docs.python.org/modindex.html
) lists out every module included in Python 2.6.
Sourceforge has all sorts of good Python modules - one that came in handy for me recently was PyExcelerator, a module for writing straight to MS Excel workbooks.  The Python Package Index, (
http://pypi.python.org/
) is also a good source of Python modules.