Take a look at MapCruncher. A very interesting new map mashup technique from the folks at Microsoft Research. It basically allows you to overlay any digital map image on top of a normal, zoomable Virtual Earth map.
Popular micro-blogging platform Twitter has announced new "retweet" feature that will be added soon, complete with a new retweet API that will allow developers to access retweets in a variety of ways. As many of you know, the Twitter API (our Twitter API Profile) has quickly become one of the most popular APIs in our API Directory.