Diego Inácio has created several geometry tools for Houdini, using Python.
Digital Tutors - Introduction to Houdini 15
Digital Tutors have released a tutorial introducing you to Houdini 15.
Houdini Demo Reel 2014
Side Effects Software has released the 2014 Demo Reel featuring the work of Houdini customers worldwide.
Tea and Cookies in Houdini - Tutorial
Tea and Cookies in Houdini is a two part commercial tutorial in Houdini, going through all the steps of the scene's creation.