According to Stephanie Strom's article in The New York Times, "To Help Donors Choose" (November 27, 2010, page B1) prospective donors should consider many factors including:-administration costs
-how much is spent on fundraising
-effectiveness in delivering services or results
-accountability
-transparency
-research on its impact
These websites may help you make an informed decision:
Charity Navigator - Charities are awarded overall ratings ranging from 0 to 4 stars.
American Institute of Philanthropy (AIP) - The non-profit's sole purpose is to help donors make informed decisions.
GiveWell - Guides small time donors by focusing on effectiveness of charities' services.