Here's a car alternator powered one.
Looks like the "stock" field strength may be causing it to draw more power than the builder can comfortably deliver. He gets winded after about 45 seconds of spinning the pedals!
So maybe my wimpy blower motor is a good thing.
Here's another alternator based one that's "not easy" from the promo for the Specialized "Innovate or Die" bicycle innovation contest: