GUIDESTAR <http://www.guidestar.org> provides access to information covering more than 1.5 million nonprofit organizations. You can verify a nonprofit's legitimacy, learn whether a contribution will be tax deductible, view a nonprofit's recent Forms 990 (filed with the Internal Revenue Service), or find out more about a nonprofit's mission, programs, and finances.
You must create a free personal registration entry & username, before you can actually use the underlying services. Additional levels of service are available for additional fees or paid subscriptions. You can decline to be placed on any mailing lists. If you enroll in the mailing list, you will typically receive just one email per month.