Diesel Electric Car
Why is there no diesel-electric car? Trains have been using this technology for decades, but to my knowledge it hasn't shown up in passenger cars yet*.
Most hybrids out there fall into one of two categories: parallel hybrid, or mild hybrid. A parallel hybrid would use the electric motor to reverse, or move the car at low speeds, but if any kind of speed or acceleration is needed, the gas engine kicks in. The Prius falls into this category. A mild hybrid, just uses the electric motor to add some extra oomph to the engine, so you can use a smaller motor and save fuel. The Honda Civic and Insight fall into this category.
In both cases though, the gas engine is the main motivator, and to my line of thinking, you might as well just slap a turbo on a 3-cylinder engine if you're gonna basically make a car that's weak, except for when you need it.
Trains on the other hand (at least the diesel-electric ones), are driven by electric motors exclusively. This is called a series hybrid. They have a diesel engine** that simply drives a generator and that's all it does. The diesel engine can basically run at a nice comfortable speed the whole time to power the generator, and you really don't need to fiddle with batteries at all - you could use them if you wanted to, but the motors can get their juice from the generator directly, or a capacitor, and you wouldn't have to worry about the battery crapping out on you after X number of years. I can't quite figure out why we haven't seen this sort of hybrid in cars yet. There must be some penalty you pay for the double conversion of diesel energy to electric energy that just doesn't factor in for trains or really large vehicles. Maybe weight?
The Tesla is the only electric/hybrid car that I find remotely interesting, but it's all battery. It's definitely cool that you'd never have to hit the gas station, but charging it up is no mean feat, and the range is around 200 miles on a single charge. That's plenty of range for most folks, and I'm sure battery technology will improve rapidly in the coming years, but if that sucker was powered by a small diesel genrator, rather than a battery, you'd be running off electricity all the time, with all the fun torque and characteristics of an electric motor, but your range wouldn't be limited since you could hit any gas station to keep the generator happy.
* The Chevy Volt is apparently a series hybrid, so we'll see how that works out. I'm reserving judgement on that one until I know a little more and see some real-world tests. I've got a natural distaste for most Chevy engineering, but every once in awhile they churn out something like a Grand National or Syclone, so you never know.
**: I'm using diesel as the fuel of choice, but gas would work too. Diesel fuel's a lot less refined than gas, and should cost a lot less (that's something else I don't understand, but that's for another post), but diesel engines are generally simpler and more reliable than their gas counterparts. There's a reason it's used for most generators and trains. Plus, you can use a variety of fuels in a diesel, so you've got some flexibility there.