A nice paper/speech from Team Obama’s ex chief economist – Christina Romer. This has been blogged about much. Krugman, Gulzar and John Taylor (responding to his criticism in the paper) have blogged about it.
Tons of research is to follow on whether fiscal policy worked or failed in this crisis. All I can say with 90% confidence is despite so much research, we can never be sure whether fiscal policy worked in this crisis.
However, this paper is a very good one (in plain english) and explains the basic problems with research on fiscal policy.