During the Spring this year I worked with Pluralsight on a Houdini course. The course has now been online for a couple of months on their site. The experience of learning to teach well and learning to make tutorials was very helpful. And, the feedback that I've received has been incredible.
If you haven't seen it, it can be found here:
And the trailer is here:
The course goes through creating a simple tree generator tool in Houdini. In order to accomplish this you learn about VEX and some mathematics. It is approximately four hours long and has scene files included that contain some additional information and tips.