XAML is going to bring some great new visualization tools to Longhorn. I vote for a “Map of the Market” tile application for the sidebar. It would be a breeze to hook up some XAML to a couple of web services and you've got some crunchy goodness. For a look at what a map of the market is look here -> http://activequote.fidelity.com/rtrnews/market_map.phtml
And by the way, if you don't have access to Longhorn bits you may want to grab notepad and a learn SVG site. XAML and SVG have some of the same concepts.
Sean