Here is a list of tools to work with the Super Mario 64 decompilation project.

Fast64 is a Blender plugin that allows for creating and changing levels and object models.

https://bitbucket.org/kurethedead/fast64/src/master/

This Blender plugin allows for modifying the Goddard (Mario's head) model.

https://github.com/SIsilicon/Goddard-ImportExport-Project

This is a new camera mode for SM64, designed from the ground up, to improve and fix all of the existing flaws with the horribly dated camera, that comes with the original game.

https://github.com/FazanaJ/puppycam