If you purchase a hybrid vehicle this year (2008), make sure to check on available federal tax credit incentives.
Here's the current IRS hybrid tax credit schedule for 2008 models.
Here's the IRS hybrid tax credit program summary.
Tax credits for Toyota models (Prius, Camry, Highlander, and Lexus models) have phased out because sales have exceeded their quotas.
Tax credits are still available for the following 2008 vehicles: Chevrolet Malibu Hybrid and Tahoe Hybrid, Ford Escape Hybrid, GMC Yukon Hybrid, Honda Civic Hybrid (reduced 7/1, phased out 12/31), Mazda Tribute Hybrid, Mercury Mariner Hybrid, Nissan Altima Hybrid, Saturn Aura Hybrid and Vue Green Line. Some new 2007 vehicles are also eligible.
Currently, the highest credit is $3000 for the Ford Escape Hybrid along with the Mazda Tribute and Mercury Mariner versions.
Note that you are not eligible for the hybrid tax credit if you are subject to AMT, and even if you don't pay the AMT your credit amount can be reduced by the AMT calculation and other credits. Here's the 2007 tax year credit form (PDF) with instructions.