Check out this winner of the 2008 red dot design awards by Nils Uellendahl,It's a concept for a helical turbine that mounts dirctly onto over-head pwoer lines .It's quite interesting in two ways :

It generates electricity directly into the line using induction

It's actually horizontally mounted ,however is actually a traditonal vertical-axis turbine.

I'm sure there are some large issues with the electrical connection and grid stability (to sa the least),and with the additional loading of the power lines ,however it's a great concept