• GuideStar
• 4801 Courthouse Street; Suite 220
• Williamsburg, VA 23188
• Phone: 757-229-4631
• Fax: 757-229-8912
• E-mail: customerservice@guidestar.org
• Web: www.guidestar.org

They have a database for over 1,500,000 IRS-recognized non-profit organizations, a very advanced search engine to help locate US-based organizations involved in various kinds of overseas relief activities, and information about grant writing.