Intro to Revit Floors from Grasshopper
Grasshopper + Colibri
How I created those branches from Grasshopper to Revit
How to get started
An example on how to automate transfering geometry from Revit to Rhino
You can access all the existing families inside a Revit file with a simple python script
Use Grasshopper to manipulate Revit (with Generative Design)