Today I was flipping through Shutterbug Magazine and came across an article that my readers might find useful. It is entitled "Photography In The Real World" (Shutterbug November 2007) and talks about two U.S. cities that are considering laws against photography on city property, including public sidewalks!
The Shutterbug article gives the link to an article written by Attorney Bert P. Krages II entitled "The Photographer's Right" which talks about photographers' rights, places that are generally acceptable to photograph, and what to do if someone harasses you about your photography. You can download a PDF of the article on his website.
If you like taking pictures these articles are worth reading. I'd also recommend keeping a copy of Bert Krages' article in your camera bag in case a self-important rent-a-cop harasses you about taking pictures in a "restricted area" (like a sidewalk).