You've probably heard the term "think tank" before, but have you ever considered using the information that comes out of one? Most think tanks have a definite perspective, so you should seek to balance whatever information you find with its opposing view. Here are some journals and think tanks to try on for starters:

Journals
American Prospect
Atlantic Monthly
Dissent
Mother Jones
The Nation
New Republic
The Progressive
Washington Monthly

Foundations
Center for Policy Alternatives
Center for National Policy
Economic Policy Institute
Institute for Policy Studies
Open Society Institute
People for the American Way

Journals
American Spectator
Human Events
National Interest
National Review
New American
New Criterion
Public Interest
Weekly Standard

Foundations

American Enterprise Institute
The Cato Institute
Heritage Foundation
Hoover Institution
Hudson Institute
Manhattan Institute

See also the University of Michigan Library's Political Science Think Tanks listing.