I *highly recommend* that you go visit Moira Allen's Web site for writers, Writing-World.com. She has an incredible resource here, including her Freelancing 101 column and archives, link resources, and a free biweekly newsletter for writers.
From there, you'll be able to find other writers' resource sites and information. There are obviously many other excellent online writing resources, of course, but too many to list on this page (that's what Inkspot was for :-)).