Flickr is almost certainly the best online photo management and sharing application in the world. Show off your favorite photos and videos to the world, securely and privately show content to your friends and family, or blog the photos and videos you take with a cameraphone.
History pin is a website that lets users place photos and videos over certain locations in the world that they have visited, a great way to to get new pictures of cities and other locations.
I just think this website is really cool. It would be awesome in a classroom to turn in things to the teacher and between students as another kind of drop-box/google doc kind of sharing.