Urban PAD includes four content editors and a city generation engine. The tool is aimed at offering editable procedural city creation through automatic content placement, real-time manual editing, and contextual adaptation. The video above is a great showcase for the application. I was lucky enough to have some people from Gamr7 demonstrate the application to me a few days ago and I was very impressed.
You can check out the trial version (or purchase the full product) at the official site of the company which can be found at http://www.gamr7.com.