In 2009, N. Gregory Mankiw (Harvard economist, advisor in the GWBush administration) passed along for consideration an demurrage-like stimulus idea from one of his students. Namely, that the Fed could declare that one year forward, some percentage of existing currency, randomly chosen by serial number, would expire worthless:

http://www.nytimes.com/2009/04/19/business/economy/19view.ht...

I've also seen the idea that a stimulus tax rebate could be offered in the form of expiring debit cards to have a similar macroeconomic effect.