This is an article from Guidestar's website:
Enforcement: IRS Addresses Political Activities by 501(c)(3)
Organizations
Earlier this year, the IRS released a report on political activity by
501(c)(3) organizations, including churches, during the 2004 political campaign.
Organizations exempt under section 501(c)(3) of the tax code—i.e., private
foundations and public charities, including churches—are prohibited from either
supporting or opposing candidates for office.
The IRS found that "nearly three-quarters of the organizations examined under
this initiative had engaged in prohibited political activities." Such activities
included supporting or opposing candidates in printed materials, on Web sites,
and from the pulpit; posting campaign signs; and giving preferential treatment
to specific candidates by allowing them to speak at functions.
The IRS is continuing its Political Activity Compliance Initiative and has
issued guidance for this year's elections. For more information on both the
report on the 2004 election and guidance for the 2006 elections, go to www.irs.gov/charities/article/0,,id=154622,00.html.