Very good question, and already well answered above by yourself, Oishi, Darlene C and Beesting.
A few things to add:
There is a very good reason why OBAMA, CLINTON & McCAIN are quiet about their associations with CFR - that is ELECTABILITY.
The short answer "What is CFR" – plain and simple – they are economic and political GLOBALISTS.
IF you wish to get an sense of what CFR is really all about, go and research David Rockefeller's involvement with CFR and Trilateral Commission and consider these statements:
"For more than a century, ideological extremists at either end of the political spectrum have seized upon well-publicized incidents to attack the Rockefeller family for the inordinate influence they claim we wield over American political and economic institutions. Some even believe we are part of a secret cabal working against the best interests of the United States, characterizing my family and me as 'internationalists' and of conspiring with others around the world to build a more integrated global political and economic structure - one world, if you will. … If that's the charge, I stand guilty, and I am proud of it."
- David Rockefeller, “Memoirs”, 2002
"We are grateful to The Washington Post, The New York Times, Time Magazine and other great publications whose directors have attended our meetings and respected their promises of discretion for almost forty years. It would have been impossible for us to develop our plan for the world if we had been subject to the bright lights of publicity during those years. But, the work is now much more sophisticated and prepared to march towards a world government. The supranational sovereignty of an intellectual elite and world bankers is surely preferable to the national auto-determination practiced in past centuries."
- David Rockefeller, June 5, 1991, Bilderberger meeting in Baden Baden, Germany
That should give you a good feel for the CFR.
(If you don't have time to research Rockefeller, here's a video that will give you the general idea of where he fits in the CFR picture http://www.youtube.com/watch?v=BbnpN07J_zg&feature=related).
Wikipedia offers a concise definition:
http://en.wikipedia.org/wiki/Council_on_Foreign_Relations
"The Council on Foreign Relations (CFR) is an nonpartisan foreign policy membership organization founded in 1921 and based at 58 East 68th Street ... with an additional office in Washington, D.C. Through its membership, meetings, and studies, it has been called THE MOST POWERFUL AGENT OF UNITED STATES FOREIGN POLICY outside the State Department." (capitalization added for emphasis)
The operative words in that link are: "it has been called THE MOST POWERFUL AGENT OF UNITED STATES FOREIGN POLICY foreign policy outside the State Department…". That is, I believe, a GROSS under-statement. It would be more accurate to say that the CFR "DICTATES" foreign policy to the government.
You could go to CFR's web site to see what it CLAIMS to be http://www.cfr.org
But to get the skinny quickly, you skip the CFR propaganda, watch this educational You Tube clip:
"The CFR controls American media" - http://www.youtube.com/watch?v=JPlvdSQ6cAM
and have more time available for your own research.
I would also add that there is a critical CFR Agenda item voters must consider in 2008 – that is NORTH AMERICAN UNION.
The government is implementing CFR's NAU agenda in stealth mode, right before our very eyes. If people don't wake up soon, it WILL happen .. it is not a myth. The evidence is readily available for anyone wishes to find it.
That topic (NAU) warrants its own question. Hopefully someone asks the question tomorrow because time is running out very quickly.