The Toyota Prius is a superior vehicle. See the Toyota Australia site to get Prius information without having to use Flash.
The Prius is a hybrid vehicle that uses a combination of Petrol and electricy for power. The battery is charged by the engine when the amount of power used for propulsion is less than the power output of the engine and is also charged by regenerative-braking (converting the car's kinetic energy into electrical energy to charge the battery).
The Prius uses less fuel, but was specifically designed to produce minimal
emissions. Most fuel efficient vehicles merely produce less pollution in
proportion to the smaller amount of fuel used, while using 1L of petrol in
a Prius will produce significantly less pollution than using 1L in any other
vehicle. To reduce emissions the spark timing of the Prius is more carefully
controlled than in most vehicles, this makes the fuel burn more cleanly (less
hydrocarbons and nitrogen oxides in the exhaust). To reduce petrol leaks the
tank has a bladder to take up unused space. When putting petrol in the tank
it usually displaces petrol vapor which escapes into the atmosphere, in a
Prius it instead decreases the size of an air bladder.
The Prius gives a more comfortable ride than most cars, it's incredibly quiet and has little engine vibration (when test driving one I couldn't determine when the engine started by sound or by feel). It uses a Continuously Variable Transmission (CVT) which means that the gear ratio is always optimal for the engine and also means that there is no sudden gear change (which involves vibration and noise in most vehicles).
The Prius also has more technical features built in than most cars, the high-end model known as i-Tech (which costs $AU9,500) more than the base version) has the following features:
If the battery has a reasonable amount of charge then the Prius will accellerate to a speed of about 20Km/h without using petrol (so you will drive out of a garage or car-park without releasing any fumes in a confined space).
Prius+ is the project to convert Prius cars to allow them to be recharged from mains power. Domestic electricity supply is cheaper than petrol for the amount of energy and also better for the environment. The California Cars Initiative aims at forcing car companies to produce hybrid cars that support charging from mains power and by a proof of concept they want to force Toyota to do it first.
The Prius Online forum is for discussion of anything related to the Prius, it's archives are a good source of Prius information.
The Hybrid Cars page at How Stuff Works has a page on the Prius.
Coastal Tech in the US sells a variety of parts and kits to enhance a Prius. Graham's Prius site