I use Flickr lots. For sharing little videos in my river blog posts, for finding creative-commons-licensed images to accompany my news stories, and for sharing my pictures with the world so that they might find their way into neat places like the Wikipedia.
And now I can embed slideshows! Woo!
Click the little arrows-in-a-box icon for fullscreen.
UPDATE: They also added videos to slide shows. They play automagically. (There are a few videos at the end of this set, if you’d like a demo.)
I love Flickr.