Local design studio and learning collective ModeLab has published a series of fantastic tutorial videos for Grasshopper. These guys have been Grasshopper experts for years and are generous enough to share some of their knowledge on the web for free.
Here is a link to their free ‘Introduction To Grasshopper’ video series. This series covers most of what we have seen in class so far and is a great resource for sharpening up on the basics. Highly recommended.
I’ll be posting a few more over the course of the term, but feel free to have a look at all of these at your convenience. They also introduce scripting in python pretty clearly, and provide a wide cross section of contemporary design knowledge. They are charging for some of the more advanced content, but lots of good stuff is available for free.