Tightening Your Plot by Layering. A great checklist for one element of rewrites.
Palm Beach Pulse: Palm Beacher James Patterson's 10 Tips to Improve Your Writing. Good advice, regardless of your personal opinions on Patterson's writing.
Etexts from University of Virginia Library: Fenimore Cooper's Literary Offenses, by Mark Twain. I started to read The Last of the Mohicans, and I have to say my opinion of the writing was much like Twain's. I recommend watching the movie instead. It has a better plot and 100% more Daniel Day Lewis in buckskins.
Marketing Tips for Authors: 15 Commandments for Getting FREE Publicity by Carolyn Howard-Johnson. Some ideas to expand your list of promo ideas.
Writer's Digest: How to Use an Outline to Write a First Draft.
Writer's Digest: 50 Simple Ways to Build Your Platform in Five Minutes a Day. A long list with a lot of ideas.
Jody Hudlund: How Much Time Should Writers Devote to Social Media? Useful guidelines based on where you are in your writing career.
SFWA: Fantasy Worldbuilding Questions. A comprehensive guide to worldbuilding for fantasy authors. Probably good for other sorts of authors as well.
Ebpublishing a Book: Promotion Stages. There are several parts to this series. It's worth a click-through.