Letting my imagination drift today, I wondered whether many people had swapped Prius drivetrains into other cars - and which thread should I find?...
Anyway, here's my answer to the original question: The Toyota Sera.
May be interesting finding space to squirrel away the batteries, but I'm sure an enterprising soul could do it. It may not quite attain the economy of a Prius (though I'm aiming low - I'd be thinking gen-1 Prius, possibly better suited to the Sera's age), but it's a way of getting Prius-like economy in a much more interesting vehicle.
Find some way of transplanting the Prius electronic speedometer and the hybrid status display into the Sera's instrument binnacle, find a space for the column shifter, and you're set.