Well the Fed is buying long term treasuries and selling short term treasuries. What will happen? The goal I think is to keep interest rates low, both short and long term, probably to spur corporations to borrow and make money and hire people. Here is an article that talks about it:
http://online.wsj.com/article/BT-CO-20110922-712602.html
The fed did promise to keep interest rates low for at least two years, and I guess this is how they plan to do it; this keeps long term rates low and the fed sets short term borrowing rates. After two years, what will happen? We will see.