Exploring Flickr, I found some photos of my hometown. I even added a comment to one. I saved a photo of a postcard showing this area of Oklahoma that used to be considered part of Texas because I may want to use it for an article I want to write for a local historical publication.
Some of my friends have invited me to a Flickr group before to view photos they took at a wedding we all attended. That's a pretty neat idea. Some libraries have their own groups and post activities going on there. I saw photos of some beautiful butterflies someone created to hang from their library ceilings.
Flickr is super, but our school filter blocks the site, as well as many other Web 2.0 tools.