Tag! You're it!
Yahoo's acquisition of Flickr gives them access to its meta-tagging community. Very, very clever. I wasn't really that aware of Flickr before this, but they've got a novel approach to solving one of the more complex problems in computing: resolving searches of non-textual data. How cool would it be to say, "find me the picture from my wife's birthday where she's wearing the funny looking hat" and have the computer bring back the right thing? Or "bring back the cool live version of that song I like that happens to be named almost exactly the same as the studio cut (which is much less cool)?" Cool, indeed.