Robert Reich offers what is to me a fairly convincing and easy to understand argument as to why our economy is stalling: Nobody is spending. Private consumers don't have the money, and deficit hawks aren't letting the government spend more.
UPDATE: The Maverick Philosopher, Bill Vallicella, himself a deficit hawk, had tongue-in-cheek suggested that if Keynesian economics worked, why couldn't we just counterfeit money and stimulate the economy that way. Actually, that might be the only option left. Anybody got a printing press?