CG Wiki
The CG Wiki by Matt Estela offers a wealth of tips and tricks that will help you build up your Houdini skills. This learning material helps you understand the nature of how Houdini works.
4 Tutorials 0:00:00
Tutorials
CG Wiki | Maya to Houdini
An exploration of Houdini from the point of view of a Maya artist.
CG Wiki | Quick Lessons
Learn / Tutorials / CG Wiki | Getting Started
CG Wiki | Houdini Long-Form Tutorials
As much as I like sticking to the short, single paragraph+gif format, now and then stuff probably requires a longer format. Those sort of things will end up here.
CG Wiki | Dynamics
Quick-tips (and some not so quick tips) that focus on dops