yt is a python package for analyzing and visualizing astrophysical simulation output from a couple simulation platforms. Check out the homepage (there's a link just above!) where we have documentation, a cookbook, and some user community information.
The repository of yt Enhancement Proposals: YTEPs
Documentation for the yt project
Active development fork for yt-3.0.
The yt website
A place to hold materials for the 2013 yt-dev workshop
The yt blog
Conda recipes for yt and other projects.
A set of scripts that load up data from various frontends and then attempts to do simple things to them.