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 yt Project
Active development fork for yt-3.0.
Documentation for the yt project
The repository of yt Enhancement Proposals: YTEPs
The yt blog
The yt website
A place to hold materials for the 2013 yt-dev workshop
The repository for yt bootcamp materials
A cookbook of scripts and recipes for yt
A collection of all the repositories and slides from the 2012 yt workshop