Nonprofit Organizations

Charity Navigator
http://www.charitynavigator.org/
Publisher: Charity Navigator

Cumulative list of organizations described in section 170 (c) of the Internal Revenue Code of 1954.
http://purl.access.gpo.gov/GPO/LPS796
Publisher: U.S. Internal Revenue Service
Catalog Record/Annotation 55061341

Give.Org: BBB Wise Giving Alliance
http://www.give.org/
Publisher: Better Business Bureau

GuideStar: The Donor's Guide to the Nonprofit Universe
http://www.guidestar.org/
Publisher: Philanthropic Research, Inc.
Catalog Record/Annotation 98802003

USA.gov for Nonprofits
http://www.usa.gov/Business/Nonprofit.shtml
Publisher: First.gov