This is a fairly subjective question the way you've phrased it; a "good" Vim blog will depend on the person. One such blog is the Vim Tips Blog. However, if you want to truly master VIM, you will likely visit them all. In addition, the vim tutor program (tutor.vim) that comes with most VIM installs is a good place to start, although I imagine you are already beyond what it has to offer.
I learned by reading vimdoc and I carried the Vi Editor Pocket Reference in my pocket to read when stuck on the bus.
I realize only my first suggestion is a blog; I am guessing you are really just looking for good resources. You may want to rephrase the question, and give details as to what resources you have found that are not meeting your needs.