From ABC:
Health and Human Services Secretary Kathleen Sebelius will announce Friday she is stepping down, ABC News has confirmed.
The president will nominate Sylvia Burwell, director of the Office of Management and Budget, to replace her.
Sebelius approached President Obama about a month ago and asked to step down after the health care sign-up numbers were released, two senior administration officials and a confidante of Sebelius' told ABC News.
...
Sebelius, a former governor of Kansas, was among Obama's earliest supporters back in 2008. Her endorsement -- over Hillary Clinton -- came at a critical time in his first race for the White House.
But the president, while always fond of Sebelius, was furious at the rollout of the health care web site. He placed blame internally on her, aides said, among others.
Publicly, however, President Obama stood by her through the embarrassment.