Not sure if folks are aware, but in addition to the Silverlight Spy tool which is a great visual tool to explore your application runtime tree and detect possible perf bottlenecks, there is also a free tool called Silverlight Inspector.
Silverlight Inspector is a free utility that lets you view your app visual tree and control/view assemblies within a XAP. This tool is an open source so feel free to download sources and post back your improvements. 

Enjoy. Jossef.