The energy producing sidewalk

http://www.fastcompany.com/1617178/toulouse-france-tests-out-piezoelectric-pavement-power
http://ecologie.blog.lemonde.fr/2010/04/14/a-toulouse-un-trottoir-produit-de-lelectricite

Here are two links to an interesting project developed by a dutch company in Toulouse. (The second article is in french for those who speak french).
The idea is to use the urban kinetic energy generated by people walking on sidewalk to power the street lights.

This project is still at the prototype stage but it could represents huge savings of energy for big cities.
They also plan to extand the idea to other structures, like soccer stadium.