Board Source – Resources for building effective non profit boards

Center for Nonprofit Excellence – Resources, consulting services and online seminars for nonprofit

Idealist.org – Tools and resources for non profit organizations

Non Profit Expert – Extensive list of articles and advice for non profits

Nonprofit Risk Management Center

The Nonprofit Board Answer Book: A Practical Guide for Board Members and Chief Executives published by Boardsource

Starting a Nonprofit: What You Need to Know – Manual from the University of Richmond (free download)

United States Internal Revenue – Forms for filing for 501(3)(c) tax exempt status in the USA

Also see Nonprofit Resource Centers and Associations by State