The Top/Bottom Customers report provides a way to printout a listing of your top customers or bottom customers based upon their sales during a given time period.  To Access this report, from the Customer Accounts Menu, click on Top/Bottom Customers in the Reporting Section as shown below:

This will bring up the following selection screen where you will be able to specify the number of top/bottom customers to report on, as well as the date range:

The following is an example of this report: