Funds for Writers is probably the best source I have found for markets, advice, grant information, contests, and more! Not only that, but the editor, C. Hope Clark, is as nice and genuine a person as you will ever want to meet. I cannot recommend this site too highly for writers. There is an e-mail newsletter that is excellent!
Writing for Dollars! is another useful site, that also has an excellent newsletter. Their website has an article database and database of writer's guidelines.
Another newsletter to which I subscribe is Publishing Poynters. This is "Book and Information-Marketing News and Ideas from Dan Poynter."
Links swapped with other writers . . .
The Wizard's Sword, by Paul Vanderloos.