Our first Office Live mash-up sample app is posted on MSDN, and Microsoft Watch wrote about it even before we we did. 

This is a nice mashup, and a great example of calling the Office Live web services apis from within JavaScript.  Basically, it allows you to select contacts from your Contact Manager business application in Office Live, and map them onto Virtual Earth right inside of your workspace. 

Chris Beiter, Office Live PM has also blogged about this.