One of my all time favorite Microsoft creation is Photosynth, which uses a technique for stitching together a lot of photos to create gigapixaletd multiperspective or panaromic view.
When I first heard about the WorldWideTelescope it was described as the Google Map of the space. It is way way beyond that.
Tuva [requires silverlight] was apparently created because Bill Gates bought the writes to the videos of Feynman delivering the Messenger lectures. And not only are the lectures themselves awesome, but the whole delivery system is beautiful too. Unfortunately it doesn't look like the technology is being used anywhere else