There is a federal tax credit ($150) for installing new high efficiency furnaces between Jan 2006 and Dec 2007. The catch is that the furnace needs to be 95% AFUE. That seems a tad high (Energy Star qualification is 90%) and removes a lot of condensing furnaces from the credit, including all of American-Standard/Trane condensing gas furnaces.
List of eligible furnaces:
formatting link
It's a short list since a lot of the condensing furnaces are 92 to 94.5 AFUE. Perhaps the companies will increase their AFUE rating by enough to get them to 95 for next year's models?There is also a tax credit for "electrically efficient furnaces" This credit is $50 and is for furnaces whose fan uses no more than 2% of the total energy use per year, regardless of AFUE.
A list of eligible electrically efficient furnaces is here:
formatting link