The good news:
*in 2006, a for-profit company plans to offer conversions of Toyota Priuses from regular hybrids to plug-in hybrid cars capable of 100 miles per gallon or more.
*Daimler-Chrysler will sell a plug-in hybrid van for 15 passengers.
The not-so-good news:
*Prius conversions will only be done in Los Angeles (info at the first link).
*The cost will be "under" $12,000, which at the upper end represents half the cost of a new Prius. My wild guess is the conversion would save one to two thousand dollars over the car's lifetime in gas costs, which is much more expensive than electricity.
*Conversions being done by a small company, not a major corporation, will have very little environmental benefit until the concept is proven successful.
So this is earlier than I expected, but little more than an experiment. I'd heard a little about plug-ins before, and CalCars has more information. Five thousand is probably the upper limit of what I could spend - hopefully the cost will drop to that level soon.
This news takes the edge off an annoying development - car manufacturers are developing hybrids that increase engine power instead of saving gas, and may benefit from tax and other advantages given to "deserving" hybrids. Evolving from hybrids, even inefficient ones, to plug-in hybrids will have to improve mileage, so free-riding muscle cars won't be a long-term problem. The best interim solution would be a carbon tax on emissions, but that's not happening soon on a national level here in the US.