The Giant Light is a durable electric bike that has garnered a good track record since it was introduced in 2002. Most electric bikes are on the heavy side, but this bike weighs only 48 pounds total, including the battery pack. Tucked behind the seat is a quick-release NiMH (nickel-metal hydride) battery pack, which powers a motor built by Panasonic. Interestingly, the motor automatically responds to the amount of pressure you put on the pedals.So if you're pedaling hard to get up a hill, the motor will give you maximum assistance. Likewise, if you're going downhill and not pedaling at all, the motor will shut off. This means the bike has no throttle, just an on-off switch. The Giant Lite costs about $1300, you can find it for sale at NYCEWheels. Apparently though, the manufacturer, Giant, has stopped production of all its electric bikes.
See some positive review for the Giant Lite over at Green Car Congress.