Personally I would wait to get any hybrid at the moment, especially if you're wanting it for environmental reasons. They are great on gas, but unfortunately the batteries for the electric motor are worse for the environment than us using gas. I've heard the batteries actually die fairly fast, and once they do, they end up being put into waste where they stay.
I would suggest looking into cars that are really good on the gas mileage for now if you have to have a new car. I have a 2006 Scion XB that gets 28mpg highway and usually 29.5-30mpg city. Yes, that's right, it does better in the city than on the highway. Plus I know they run fairly cheap, and are reliable.
If you have your heart set on a hybrid then between the two, toyota's prius is supposed to be better. Currently other companies are trying to catch up with this trend, and will be putting out more hybrids soon.