100 Top U.S. Foundations.
Ranks by assets or by giving. Who wants to be the first to pull these into a spreadsheet and rank them by percentage of assets given?

AnyWho Toll-Free Internet Directory
A useful tool for finding U.S. nonprofits as well as companies.

Associations on the Net
Collection of 700 sites with information on associations. Search or browse. From the Internet Public Library.

BBB Wise Giving Alliance
Formerly the Philanthropic Advisory Service of the Better Business Bureau. It has merged with the National Charities Information Bureau. Has information on selected nonprofits, from the Council of Better Business Bureaus Foundation.

Common Wealth
A rich collection of articles and studies on nonprofits from The American Prospect. Links to interesting recent reports on the ways and means of philanthropy.

Council on Foundations
Links to sites of about 200 of the largest foundations. Click on "Links."

GAO report on tax-exempt organizations
In PDF format, this GAO report from April 2002 gives a detailed introduction to the IRS Form 990 and regulation of nonprofit organizations.

GuideStar
Detailed information on more than 40,000 nonprofits, and summary info on more than 700,000 U.S. charities and nonprofits. On most you get only the name, address, amount of income and assets. Now adding info from Form 990, the U.S. nonprofit tax return. Searchable by keyword, type, state, revenue range, and tax ID number.

How to read the form 990
A step-by-step guide to dissecting Form 990, the annual tax return which (most) nonprofit organizations in the U.S. have to make public. From Peter Swords, former executive director of the Nonprofit Coordinating Committee of New York.

How to read your form 990
A guide to the IRS form for nonprofits, from the point of view of a filer, the American Federation of Teachers.

InfoSpace
Offers a reverse directory, yellow pages, white pages, fax numbers, etc.

IRS all tax forms
Instructions and copies of all IRS tax forms.

IRS Exempt Organization Search
From the horse's mouth. Current information. Search by name or city/state.

IRS other info on non-profits
An IRS directory of info on "tax exempt organizations."

IRS Tax Forms for Nonprofits
See the forms they file (annual 990, tax on unrelated business income, etc).

National Center for Charitable Statistics
The best site for information on nonprofits. Now adding copies of IRS Form 990, the nonprofit tax return, for U.S. tax-exempt organizations. Also many databases, state profiles of nonprofits, other guides.

National Charities Information Bureau
Now merged with the Better Business Bureau as BBB Wise Giving Alliance.

NonProfit Gateway
This interagency site from the U.S. government is designed as a central starting point to help nonprofit organizations access online Federal information and services. Linked to all Cabinet departments and many agencies, it contains information about grants, regulations, taxes, and other services as well as information on a wide range of other topics and programs.

Online Librarian
You get one free question (and answer) a week from the Foundation Center librarian.

State and Local Foundation Directories
An excellent new bibliography of state and local lists of foundations, from Foundation Center.

The Foundation Center
Much information for and about foundations. Check out its links to nonprofit resources.

The Foundation Directory
The Bible of grantmaking, a dead-trees book described here, it's listed here along with other databases and guides, from the Foundation Center.

Thomas Register
Nonprofits have trademarks, too.

Understanding the Form 990
Guidestar's guide to the IRS form for nonprofits.

WHOIS
Maybe you can find a person or organization by searching for its Web domain names, such as creator.org or elvisisalive.com. Listings include name, address and E-mail address. Search in the registry of top-level domains (only .com, org., .net). Use just the domain name (yahoo.com), not a full URL (www.yahoo.com or http://www.yahoo.com). Note the help file for other options, including searching by company name.

World Directory of Think Tanks
Japan's National Institute for Research Advancement has a massive list of major think tanks worldwide -- 320 from 77 regions. This site provides contact information along with short descriptions of what the think tank's focus is, lists of staff and publications, and brief background information.

Your Guide to IRS Form 990
A guide to the IRS form for nonprofits, including its limitations, from the Charities Review Council, of Minnesota.