Diego Inácio has created several geometry tools for Houdini, using Python.
Intro to Procedural Modeling in Houdini
John Moncrief has created a tutorial introducing us to procedural modeling in Houdini.
Houdini for Games - Frima Studio
See how Frima Studio use Houdini to generate content for their games.
Side Effects Software have announced the release of Houdini Indie for independent animators and game makers.