Here's an article about some aftermarket plug-in hybrid conversion choices.
http://blog.wired.com/cars/2008/10/plug-ins-arent.html
ConVerdant Vehicles (New England) looks interesting.
http://www.converdantvehicles.com/index.html
Nick Galaday
Vernonia, OR 97064-1180
___Energy Conservation
.....saves more than energy!