Here is a great list of assorted resources and references for writers that I recently came across.
150 Writing Resources
Some of the categories for the sites are:
Almanacs (like Answers and Black Facts Online, a good starting point for research though not listed as credible enough to cite as resources)
Citation styles (like APA or Chicago)
Dictionaries (I love my Webster's dictionary and thesaurus that is installed on my hard drive but online dictionaries are very useful as well)
English language skills (like "The Elements of Style")
News media resources
Writing software (like Blogger and Open Office, both of which I love)
Bookmark this list for future reference!