Below are some resources I refer people to all the time for information and assistance in creating and running your nonprofit organization.
Stanford Center for Social Innovation

NOLO Press, How to Form a Nonprofit Corporation in California:
Authenticity Consulting, Carter McNamara, Field Guide Series:
Independent Sector is a leadership forum for charities, foundations, and corporate giving programs committed to advancing the common good in America and around the world:

The Chronicle of Philanthropy:

National Committee on Planned Giving:
Board Source (Governance Series) focuses on building your nonprofit board:
Guidestar - Connecting people with information about nonprofits:
This site provides the Nonprofit FAQ, a compilation of frequently asked questions, and their answers, based on on-line communications about nonprofits (mostly in the US) beginning in the early 1990s.
And for all your tax questions of course: