It would cost about $7 to drive in midtown, thereby hopefully reducing congestion and pollution in tandem. Hybrids would be exempt. Not sure yet how they'd deal with taxis.
It's been very successful in London:
In London, where congestion pricing began in February 2003 after a year of planning, traffic has been reduced by a third and some bus lines are moving twice as fast. Officials are so satisfied that they intend to nearly double the size of the congestion-pricing zone in 2007. One thing seems certain: New York would not charge nearly as much as the $14 it takes to drive into London's financial district during the day.