Grammar Girl's Quick and Dirty Tips for Better Writing (Quick & Dirty Tips) by Mignon Fogarty
Go Publish Yourself - Membership required for full access, but they also offer a lot of resources in areas such as printing, ebooks, and marketing.
Gropen Associates - “Reference Desk for Publishers,” everything from budgeting to production and distribution.
Goins, Writer - Writing and creativity tips, plus a list of resources.
Go Teen Writers - Writing tips for teens with guidelines, tips, and a newsletter.