These two resources were recently brought to my attention. Current students may find them very useful for those upcoming final papers and projects (including your paper for City Wild!); everyone else, feel free to browse!

Green Cities: Good Health 
University of Washington, College of the Environment
A comprehensive overview of benefits of urban nature, with many links to other resources and an extensive bibliography for further reading

The Nature of Cities
An online magazine/blog/community about all aspects of, well, nature and cities