When I was a little stuck on the fourth project on D3 because of the color scale and legend, I found this class on Coursera and I audited it.
As a visual learner, I really like that this class shows a lot of examples. The class might be too slow for some people (go for 2x speed), but I like how it breaks down the project into smaller function and show a different way of doing things than the FCC sample.
Just wanna share it 
Please remove if this post is not okay