Favorites - updated 3/26/14

1. Metroboard: This has a 600w motor, and 36v lithium ion battery. The best part: it only weighs 19 lbs. That means that it's nice and portable if you want to bring it places. It gets really good reviews, and the company even goes to the trouble of comparing it's boards (all metroboards pretty much the same) side by side with the competition. 
Price: $1100, after the add-ons, which I think are worth getting (barings and bigger wheels).

2. Super Turbo 1000-Lithium Electric Scooter (Black): This thing is a beast. 1000 watt motor, 48 volt lithium ion battery takes you to a max speed of about 32 mph. The reviews on this thing speak for itself, with a perfect 5 stars on 13 reviews on amazon.
Price: $1000

 3. Prodeco V3 Phantom X2 8 Speed Folding Electric Bicycle, Matte Black, 26-Inch/One Size : This thing just looks really fun and gets fantastic reviews. You can't go wrong here, provided you have nearly $1400 bucks to spare, and space to store this thing. 500 watt motor, 38 volt lithium battery you will have a really nice piece of equipment that isn't too heavy. 20 mph max speed. 40 reviews at 4.5 stars out of 5 speaks for itself. People really like this thing. The fact that it has pedals means you can get a lot more milage per charge, since you can help the battery out by using your own energy to move the bike forward for a range of about 28-38 miles per charge.
Price: $1355

4. 500 Watt Electric Speed Go Skateboard-black : I don't care that it doesn't have reviews yet and may or may not be cheaply made. This thing just looks awesome to me. According to the specs, it weighs only 39 lbs, has a 500 watt motor, and a 36 volt lithium ion battery. They claim it gets 17 miles to a charge and goes up to 20 mph. At around $700, that seems like a good deal in terms of power, weight, portability, and fun. One concern is that it says that the 20 mph is weight dependent, and the max load is 200, so if your flirting with the max, as I am, you are not likely to be cruising at 20 mph the whole time, especially not up hills. I'm okay with that, since the whole idea of standing on the board seems a bit precarious to begin with. If it breaks, I guess you can take it to your local garage and have him work on it if it's something you can't fix yourself. Since it has no reviews and is new, proceed with caution here and not expect a perfect piece of machinery at this stage.
Price: $699

I think you can pick this up at Sears for around $669.

5. Flykly smart wheel: it's not a bike or a skateboard, but its pretty cool anyway. It's a wheel that easily snaps on to any bike, and turns it into a pedal assist 250 watt 36 volt lithium ion e-bike with a top speed of 25 mph. No wires or complicated construction required. The wheel syncs with your smartphone to tell you the speed, battery power left, etc. One of the coolest things is a GPS that is inside the wheel which tells you where it is located in case someone tries to steal it (if you live in NYC, they probably will, I know because I got my first electric bike stolen). If you're worried about e-bike laws this wheel seems like it won't be easily identified as an ebike wheel, and since there's no throttle, that won't give you away either. 
Price: This isn't out yet, but can be pre-ordered for $590, which seems like a good deal. 


Note: I only included bikes and boards with lithium ion batteries because they are the best kind of battery. I've owned a couple of e-vehicles with lead acid batteries (e-zip 750 and raw motors 500watt ebike), and while they were super fun at first, the lead acid battery is all but useless after 1 year. So unless you plan on going to the trouble and cost of constantly replacing the super heavy battery on your mediocre lead acid bike, it's just not worth investing in one. As soon as you ride an electric vehicle, you are going to like it way too much to want to deal with the down side of the lead battery (heavy and gets weak really quickly).