Python / Cython resources
Python - docs, FAQs, wiki, language, library, modules, packages, quickref, python-dev, repo, tracker.
Library tools - errno, functools, gettext, glob, inspect, itertools, locale, logging, multiprocessing, optparse, os, os.path, pdb, pickle, re, shutil, string, subprocess, sys, tabnanny, threading, time, timeit, trace, traceback, urllib2.
Other tools - py2depgraph, pycallgraph, PyChecker, PyFlakes, Pylint, Snakefood, XDot.
Tutorials, books, etc.
Dive into Python by M. Pilgrim.
How to Think Like a Computer Scientist: Learning with Python by J. Elkener, A. B. Downey, and C. Meyers.
Python for Software Design by A. B. Downey.
Articles, HOWTOs, etc.
decorator by M. Simionato.
Functional Programming HOWTO by A. M. Kuchling.
Regular Expression HOWTO by A. M. Kuchling.
Static Code Analyzers by D. Hellmann.
Packages included in Sage
matplotlib - 2D plotting - docs, examples, gallery.
Mercurial / hg - Source control manager - book, extensions.
MoinMoin - Wiki engine - extensions.
Pexpect - Spawn and control processes.
PyCrypto - Cryptographic algorithms and protocols - current.
SQLAlchemy - Database toolkit - docs.
ZODB - Object database.
Google App Engine - Web framework - docs.
Python Imaging Library / PIL - Image processing - docs.
Pyjamas - Web and desktop framework.
PyNIfTI - Medical imaging.