Also known as a "527 group", a tax-exempt organization that is created to influence elections.
The name comes from a section of the United States tax code.
These organizations are not regulated by the Federal Election Commission. Therefore, people who would normally contribute millions of dollars to a candidate, could legally contribute to one of these groups instead.
Examples of 527s:
"Swift Boat Veterans for Truth"
"Voices for Working Families"
"Americans for Progress and Opportunity"
"Laborers for Labrador Retreivers"
"Strippers for Subsidized Silicone"