This is a module full of tools to analyse the outputs of InterStellarGadget, and was used for my MPhys project. The thesis for that project is available here.
You can run common.py in a directory full of GADGET snapshot files and it should produce some nice movies and plots.
Please see the file itself for more information.
tests.py uses the included test data to produce some nice plots, take a look at it -- it should help you understand the way that the module is structured.