I hadn't seen this kick-ass feature on flickr that lets you add a note to your photograph which shows up when you mouse-over it. Here's an example of it in action. How cool is that?
I love all the rich UI's that people are building.
By the way, with all the talk about ajax, one really cool feature would be an auto-save for any large text boxes (like when I'm blogging or emailing). That way if I lose connectivity, accedentally close my browser window, or anything else, I don't have to worry about losing my data. Does anyone already do this?