Writers love to read about writing. I think it's more a reflection of our own neurosis than any genuine desire to improve ourselves. This is made especially apparent when one considers the crap that's out there.
That being said, I've done a search and have found some interesting links. Probably the most interesting being the one from the Guardian, which compiles several rules about writing written by writers. Among those listed are Elmore Leonard, Anne Enright, Neil Gaiman, and Richard Ford. Some of the rules are on the light side ("Don't be one of those writers who sentence themselves to a lifetime of sucking up to Nabokov" "Do not place a photograph of your favorite author on your desk, especially if he is one of those who committed suicide") and some are bit more serious ("Do it every day. Make a habit of putting observation into words).
I also spied an interesting essay by Molly Young, who wrote in response to above Guardian article. I even found an interview with Ms. Young asking her about the piece she wrote in response to the article.
Some of the essays I read fell into the realm of education. This one was fascinating. It demonstrated how writing badly was a way to demonstrate or to learn how to write well. Don't laugh, take a look and think about it. The opening paragraph alone is worthy of repeating:
"Deliberately writing badly can be an effective way to learn to write better, because knowing when it's bad is an essential element in knowing when it's good. In terms of learning theory, the negative examples produced by writing badly help define what the positive examples are (Davis et al. 227)."