See http://www.astropython.org/resources for a nice up-to-date list of python astronomy resources.

Below is a (no-doubt incomplete) list of cosmology-specific resources I've come across.

CosmoFisher by David Ventimiglia

http://dventimi.github.com/CosmoFisher/

"Python code 'to help create, manipulate, visualize, and gain value from Fisher information matrices'

cosmology module in esutil

http://code.google.com/p/esutil/

Mostly distance measures.

James Schombert's version of Ned Wright's Cosmology Calculator

http://www.astro.ucla.edu/~wright/CC.python

cosmocalc by Tom Aldcroft

http://cxc.harvard.edu/contrib/cosmocalc

Improved version of CC.py with programmatic interface. Not designed for use with numpy.

CosmoPy

http://www.ifa.hawaii.edu/cosmopy/

Interface to the powerful CAMB software for CMB anisotropy calculations.

PyCos

http://www.astro.princeton.edu/~msshin/science/code/index.html

Source not posted.

Andrew Becker's cosmology-1.1.py

http://www.astro.washington.edu/users/becker/python_software.html

OO interface to distance measure calculations.

Taro Sato's Python version of kcorrect by Michael Blanton

http://nomo17k.wordpress.com/2009/08/02/kcorrect-kcorrect-python-port-project/

k correction and photometric redshifts.

Ned Wright's Cosmology Calculator

http://www.astro.ucla.edu/~wright/CosmoCalc.html

CAMB: Code for Anisotropies in the Microwave Background

http://camb.info/

INITIATIVE FOR COSMOLOGY

http://icosmo.org/cgi-bin/Interactive_Step1.cgi

Online and IDL calculator