Several days ago Toyota announced that they are developing plug-in
hybrids.  These are hybrids with larger battery packs.  They're
designed to be plugged into a socket and charged at night, then you can
drive up to, perhaps, 8 or 10 miles on battery power alone before the
gasoline motor kicks in.  You should get many of the benefits of an
electric car, but still retain the long range and ability to "fill her
up" at gas stations during those extended highway trips.

Some people have already developed conversion kits to make the exsting
Prius into a plug-in hybrid.  It does void your warranty,
unfortunately.  It seems likely that these homebrew kits, plus the
higher price of gasoline, spurred Toyota to give plug-ins a proper try.

As with pure electric cars, batteries are the limiting technology.  Not
only are they expensive, but the discharge cycle of an electric car is
much more demanding on batteries, and they are prone to degrade faster
than the batteries in a "conventional" hybrid.

One interesting aspect of this is that it could eventually pave the way
for fully electric cars.  I can imagine future models that move more
and more work onto the electrical system, with improved battery
technology, until it becomes practical to jettison the gasoline engine
completely.

Now, speaking of electric cars. . .   I was floored by the recent
unveiling of the Tesla Roadster.  It's going to be an expensive car and
very much a toy rather than a practical, economical car -- but what a
toy!  You are looking at 0-60 MPH in 3.7 seconds, upwards of 250 miles
driving range per charge, and top speed about 135 MPH.  It appears that
battery technology is just beginning to edge over the line of adequacy
for electric cars.  Storage technology (both batteries and
supercapacitors) is being heavily researched around the world, so it's
only going to get better.

I can imagine five or six years from now, electric cars becoming really
practical.  The benefits can be huge.  These cars can get energy
efficiency equivalent to 135 MPG.  Mechanically they are very simple:
no complex engine to repair or keep in tune, no oil changes, no filters
or hoses, no spark plugs, no exhaust system.  They could have a long
lifespan with very little maintenance.  Based on some storage
technology that's in labs today, it's just possible they might achive
400-mile range, fast recharge, and much reduced battery degradation
over time (or practically none, in the case of supercaps).

We aren't there yet.  But I'm beginning to feel optimistic, there's a
light at the end of the tunnel for electric cars.  It's getting close
enough to think about buying one sometime before I get onto Social
Security.  :)