I don’t know if anyone else here reads Hacker News , but I just came across this article . Showing a diagramatic view of Japanese sentence structure seems extraordinarily insightful.
This doesn’t give a full understanding of Japanese grammar, which is something that is best learned through application, but it provides a strong picture through its simplified representation. It seems to intend to provide you with 80% of the knowledge you will need to understand Japanese grammar. I found it provided me with a similar level of understanding that Koichi provides in TextFugu. Maybe his gradual progression from one stage to the next gives a more solidifying knowledge, however.
Here  is a current (as of 2017/03/19) discussion.
[Edit] This is also a textbook  I have not heard mentioned before.
I moved this topic from Japanese Language Grammar to Japanese Language Resources, as I feel it’s more appropriate, considering the focus of discussion in the replies.
For those looking to purchase this textbook, an audiobook version is available.
A comment about the audio is available below: