In February of 2009,  President Obama signed a huge stimulus bill that included up to $1500 for energy saving home improvements, including new windows and doors. 
 
New Window replacements must have a U-factor and Solar Heat Gain Coefficient (SHGC) less than or equal to .30.  You can find the rating on windows U-factor and SHGC by checking the National Fenestration Rating Council (NFRC) label.
Qualifying windows must be purchased between February 17, 2009 and December 13, 2010 to be eligible for the tax credit.  The maximum credit is $1500 for all homes.

Learn More by visiting Energy Star.

Energy Trust of Oregon offers additional rebates and credits for homeowners who make energy saving improvements.

Learn More