The Federal Reserve announced plans to unleash more stimulus Thursday, in its third attempt at a controversial program to rev up the U.S. economy. The policy, known as quantitative easing and often abbreviated as QE3, entails buying $40 billion in mortgage-backed securities each month. The end date remains up in the air, as the Fed will re-evaluate the strength of the economy in coming months. The Fed is wasting no time. The purchases begin Friday and are expected to total about $23 billion over the remainder of September. In addition, the Fed also indicated that it plans to keep interest rates at "exceptionally low ... (full story)