I have used Wikimedia Commons many, many times to find free-use imagery. It’s amazing what you can find there. Now it contains some of my photos as well. I didn’t realize how easy it was to upload images to this source until a friend pointed that out.
So far I’ve uploaded several photos taken recently in New York: the Vanderbilt statue, the Freedom Tower, and the skyline by night from atop the Empire State Building (featuring the Bank of America Tower and the Chrysler Building).
Previously I’ve used Google’s Picasa to share Creative Commons photos. In my photo stream there, you can find images of Tea Party events, several Colorado politicians and activists, and more. Check it out!