This is so far the most informative discussion on the (in)famous fiscal stimulus I've happened onto: a recent, 1 hour long, panel discussion within the Myron Scholes Global Market Forums at the University of Chicago Booth School of Business, having as panelists U. of Chicago professors John Huizinga, Kevin Murphy and Bob Lucas. My favourite is Kevin Murphy (and here I am in total agreement with Steven Levitt, see below for his blogpost and more details), though Huizinga and Lucas have also extremely interesting and pertinent points. Don't miss the questions-answers part in the end either, again particularly for Murphy's answers. Here's the video, and here are the PDF presentations of each of the speakers (to be used while listening to the respective speeches): Huizinga's, Murphy's, Lucas's.
Hat tips to Greg Mankiw and Steven Levitt.