The treadmill motors might be your best bet, given that you don't want
to spend much time. The RPM needed to get 12-15 volts will probably be
reasonable. Cut your blades from 4" PVC pipe, or just buy a set of
carbon-fiber ones from hydrogenappliances.com. This will get you
generating in a minimum amount of time, then you can decide if you want
to get into generating in a bigger way.

Martin