One of the major complaints from consumers about hybrids is that most people can't manage to get anywhere close to the EPA ratings.
Starting for the 08 model year, the EPA is adjusting their mileage numbers to reflect something closer to real-world numbers. Of note is that the testing procedure has not changed - the EPA is basically running the existing numbers through a correction formula to get the new ratings.
Also of note is that the fuel consumption really has not changed. The EPA is merely trying to give consumers a more realistic expectation when they are comparing vehicles.
So, here is what the changes give us (when available, comparable non-hybrid models are also listed). The each set of numbers are city/highway/combined ratings. The first set are the old ratings while the last column are the ratings under the new formula.