Check out these recommended, reputable, relevant resources for inquiry into how cities can become sustainable:
Green Infrastructure Ontario: group focused on sustainable cities. Lots of info.
City of Ottawa Environmental Policy and Planning
Government site with a huge variety of sustainability topics
Vancouver's sustainability plan: "Greenest City"
TV series about water use and sustainability issues - great urban info
Sustainable Communities Info and Initiatives
Local organization focused on city sustainability issues
Online science encyclopedia and library. Click for password.