As someone who actually has a degree in economics, I don't think it is as simple as spend, spend, spend.
That WOULD be true if the problem was a lack of demand. However, the problem is a lack of credit.
This is why the Federal Reserve has been trying to get people to LOAN, LOAN, LOAN. By providing money to banks, etc.
Every dollar, however, that the federal government spends is a dollar of money that is loaned to the federal government, RATHER, than being loaned or invested in the private sector.
Since the problem is one of credit, the best thing the government can actually do is to stop borrowing money. Government debt is taking money AWAY from the private sector and preventing the creation of jobs.
So, the solution is not to spend more money the government doesn't have. It is actually to spend less money, so that investers will be forced to invest in the market and create jobs, rather than spend money on government bonds.
Keynesian economics is NOT straight forward in a global economy. If the US stimulates its economy, a good portion of the multiplier goes overseas.
Likewise, if stimulation of the markets from government spending, is offset by the government borrowing the money to do it, there is a corresponding loss to match the gain.
If the government simply creates new money from thin air to stimulate the economy (true, pure Keynesian economics in the most simple form), it would not work as Keynesian predicted because the government debt market is not a compeditive market. A few key players, mainly China, own a substancial portion of US government debt, and an action to significantly reduce the value of that debt, would lead the the responce of a dumping of that debt. That, in turn, would significantly raise interest rates on the debt and such an action would, at the best cause a depression, and at the worst a situation far worse than the great depression.
Bottom line is that Keynesian economics ONLY WORKS in THEORY and only in a CLOSED or mostly-closed market that is compeditive.
In real life, it is not that simple.
In my opinion, the best thing the government can do for the economy is balance the budget.