This solar wind bridge concept could power 15,000 homes and grow vegetables. Via Engadget:

Why just use solar power or wind power when you can use both? Designed by Francesco Colarossi, Giovanna Saracino and Luisa Saracino as part of an Italian design contest to re-imagine a decommissioned bridge (for which it placed second), this so-called Solar Wind concept would have solar cells embedded in the roadway (an idea that's already catching on) and an array of 26 wind turbines underneath, which the designers say could produce enough energy combined to power 15,000 homes. To make the design greener still, the designers have even included a "green promenade" that would run alongside the road, which they suggest could be used to grow fruits and vegetables that'd then be sold to folks driving by.