http://www.silverlightbuzz.com/2009/08/03/obama-to-jfk-deep-zoom/This example of silverlight's deep zoom capability is really really good. The easiest way to zoom in is by double clicking the photo of the previous presidents in the background as they appear, while single click panning to adjust your focus.
The smoothness is just awesome, and even on my slow connection it took hardly any time to load.