Former Treasury Secretary Timothy Geithner has landed in the private sector, taking a job as president of the private equity firm Warburg Pincus, the firm announced. Geithner, who was president of the New York Fed at the outset of the financial crisis and has spent much of his career in the public sector, will take an active role in managing the firm. Geithner worked closely with Treasury Secretary Henry Paulson and the chairman of the Federal Reserve, Ben Bernanke, to devise a response to the crisis while serving as head of the Federal Reserve Bank of New York.