American Society of Journalists and Authors
"The nation's leading organization of freelance writers."

Editorial Freelancers Association
A resource for editorial freelancers, with chapters in several U.S. areas: New York City, Boston, Mid-Hudson Valley, Philadelphia, San Francisco. Membership can be expensive, but it provides health benefits, job postings, reduced tuition to EFA classes.

National Writers Union
The union for freelance journalists working in U.S. markets.

Worldwide Freelance Writer
Writer's guidelines for freelance writing in many countries, as well as advice, writing software, etc.

Writers' Guidelines Database
Rules for freelancers and contributors at many publications.