From the IRS website:
Beginning in 2008, small tax-exempt organizations that previously were not required to file returns may be required to file an annual electronic notice, Form 990-N, Electronic Notice (e-Postcard) for Tax-Exempt Organizations not Required To File Form 990 or 990-EZ. This filing requirement applies to tax periods beginning after December 31, 2006.
Small tax-exempt organizations, whose gross receipts are normally $25,000 or less, are not required to file Form 990, Return of Organization Exempt From Income Tax, or Form 990-EZ, Short Form Return of Organization Exempt from Income Tax. With the enactment of the Pension Protection Act of 2006 (PPA), these small tax-exempt organizations will now be required to file electronically Form 990-N, also known as the e-Postcard, with the IRS annually. Exceptions to this requirement include organizations that are included in a group return, private foundations required to file Form 990-PF, and section 509(a)(3) supporting organizations required to file Form 990 or Form 990-EZ.
This new requirement should help opposition researchers find updated address information on smaller nonprofit organizations which are exempt from filing annual information returns. The e-Postcard will require organizations to provide the following information:
• Organization’s name,
• Any other names the organization uses,
• Organization’s mailing address,
• Organization’s website address (if applicable),
• Organization’s employer identification number (EIN),
• Name and address of a principal officer of the organization,
• Organization’s annual tax period,
• A statement that the organization’s annual gross receipts are still normally $25,000; or less, and
• If applicable, indicate if the organization is going out of business.
Note that "The Pension Protection Act requires the IRS to revoke the tax-exempt status of any organization who fails to meet their annual filing requirement for three consecutive years." Since there is little or no enforcement concerning nonprofit organizations it remains to be seen if this will actually happen.