Toyota first demonstrated a futuristic hybrid concept vehicle at the Tokyo Auto Show in 1995. The car, which consisted of an electric motor connected to a regular gasoline engine, was called the Toyota Prius. Hybrid skeptics —both at the show and afterward—are now silent, as cumulative global sales continue to surpass all expectations. Which of today's wild and wacky hi-tech enviro car concepts will become tomorrow's practical fuel-efficient vehicles? Let's take a look at some contenders.