I have long used card sorting with students as a method of organizing material for a new site. Now Boxes and Arrows: Card sorting: a definitive guide this guide appears to explain the technique. It is also a good method of sorting through the existing material on a badly organized site for a site makeover.
When all the students in a classroom sort and explain their thinking for a set of cards, you get some idea of what the results might be in a real-world situation where the salesmen, the managers, the programmers, and the support staff organize cards for a company site. It gives a dramatic example of the idea that different users have different goals when they visit a site and designers must organize material and navigation to anticipate those scenarios in their preliminary site planning.