Diego Inácio has created several geometry tools for Houdini, using Python.
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.
Jean Claude Nouchy - Houdini FX TD Showreel
Jean Claude Nouchy has posted his Houdini FX TD showreel, showcasing work from several high tier films.
Houdini - Demo Reel 2011
Check out this demo reel showcasing some of the best work achieved with Side Effects Software's Houdini.