The IRS has a tool on their website that can help you look up charities and other nonprofits.
The Exempt Organizations Select Check can help you three different ways:
1) It can let you see if a charity is eligible to help you receive tax-deductible donations.
2) It can let you know if the tax-exempt status of a nonprofit has been automatically revoked because it didn’t file its annual information return (such as Form 990) for three consecutive years.
3) It can look up information that’s found on Form 990-N, also known as the e-postcard.
To locate the Select Check tool, go to irs.gov and type “charity” in the search field.