Around here, we call those the "Pious" because most of the owners bought them because they think they are saving the planet. Actually, the batteries reportedly cause a lot of pollution where they are manufactured ... But I digress.
If you actually pencil out total ownership costs, not just gas mileage, you seldom actually save money overall by buying a hybird car. It is almost always cheaper to buy a conventional car with great mileage, such as the Corolla or Yaris or a Scion, as others have mentioned here.
Plus, there are some high maintenance costs down the road with the Pious, and apparently some major headaches for some owners as well. You might read through some of these nightmares experienced by Pious owners before plunking down your hard-earned cash on one. There are pages and pages of very serious and costly problems owners have had:
Consumer complaints about Toyota Prius