Here is a quick guide to finding information on nonprofit organizations:
GuideStar is a database of nonprofit organizations which are identified as 501(c)(3) public charities. GuideStar requires registration, so set up a free login and password for access. Some portions of the site require payment, but you can retrieve the 990 form, which the organization is required to file with the IRS, without charge.
The Foundation Directory Database (access restricted to current Columbia affiliates), published by the Foundation Center, enables you to search both for grants and for foundations which make grants (note that the “990 Search” is not part of our subscription).
For a guide to other nonprofit resources at Columbia University Libraries, check out the Business Library’s guide to Nonprofit Organizations, which includes reference books and directories, links to useful databases, and websites of interest.
Last, but certainly not least, the Foundation Center’s New York library, near Union Square, is open to the public, and provides access to databases which list donors to organizations, individuals and their board affiliations, and much more.