It is a bit trying to separate the economic anaylsis of President Obama's jobs speech and the proposed American Jobs Act, but some economists worked overnight to cut through the talk and look into the details.  Mark Zandi, chief economist of Moody's, has come out with the headline worthy number of 1.9 million.  That's how many jobs he says the jobs plan would add.  He also projects GDP growth of an additional 2 points next year if the act is passed.  You can read the analysis here (subscription required), or Politico's coverage of the report here. 

Menzie Chinn took a stab at textbook analysis of the president's proposals.  At Econbrowser, Chinn writes that, following "textbook" thinking, the president was right to focus on the short run output gap, as demonstrated in the below figure:

Using the CBO's measure of potential, the lost output has been $2.8 trillion (Ch.2005$) through 2011Q2. Using the WSJ mean forecast, another $1.4 trillion will be lost by 2012Q4. The CBO-implied output gap as of 2011Q2 is 7.1% (log terms). Using a cubic in time trendline, the gap is still 3.4% (and then one has to believe that output was above potential 3.3% in 2007Q3).

Extended unemployment insurance, extension of the payroll tax holiday [CBPP], and infrastructure spending are all means by which aggregate demand can be sustained. To the extent that extended UI and payroll tax holiday benefit lower income/liquidity constrained individuals, the marginal propensity to consume is relatively high and hence the multiplier fairly large. Investment in infrastructure also makes a lot sense given the multiplier is fairly large for direct spending.

Read Recovery, or Replaying 1937 (and 2008)? here.