The NY Times has an article about how the Toyota Prius has been modified into a plug-in hybrid. Prius cars sold in Europe have the ability to run solely in battery mode, but this feature isn’t available in the Prius cars sold in North America. In additon, not all hybrids are battery/ICE, German engineers have made a hybrid fuel-cell/flywheel bus and there was also a report of a hybrid battery/compressed air car. Also, out of the standard battery/ICE hybrid cars, there are different classes of hybrids which reflect the amount of battery power that is being supplied to the engine.
Even with the increased fuel efficiency and high gasoline prices, hybrid cars are still more expensive over their lifetime than a regular car of the same size. A more recent development is hybrid trains such as those made by RailPower. These trains are diesel/battery hybrids. There is actually political will to limit emissions of trains, and so hybrid trains are thought to be the next major transportation revolution.