I don't know if you've ever seen a demo of the "Dynamics NAV 2009 SP1 Treemap"-addin. No? Here is a screenshot:
It's actually another view on the "Customer List". People who have ever seen the Performance Point "TreeMap"? This one is quite the same. It gives you a customer list with the most important customer bigger then less important customers. In fact, you can set this up yourself with the parameters on top of the graph.
This is Microsoft's explanation:
The Treemap Business Data Visualization for Microsoft Dynamics® NAV provides a unique view on business data. It can provide insight from different data perspectives and can be used to help identify outliers and actionable items. Combined with histogram-based visual filtering and integration into business logic and the user interface (UI) of the RoleTailored client, this is a powerful tool for end users.
This AddIn is now available for Microsoft Dynamics NAV … officially (and supported!). You (partners) can find the application files here and the whitepaper here.