Card Sorting is a technique used by myself and many Information Architects to categorize information and sites; has other applications too.
Donna Spencer, with Boxes and Arrows, wrote a fantastic article titled: “Card Sorting: A Definitive Guide“. If you are interested in this technique, I highly recommend reading this article.
Information Architecture Institute
FeedBurner
Here’s a budget-friendly online Card Sorting tool with built-in data analytics: http://www.usabilitest.com/CardSorting