Usability and user experience testing is vital to creating a successful website, and only more so if it’s an e-commerce website, a complex app or another website for which there’s a definite ROI. And running your own user tests to find out how users are interacting with your website and where problems might arise is completely possible.
UXSort - card sorting tool to enable user experience professionals to plan card sorting activities and view clustering dendrogram. It supports sorting up to 1000 cards, drag and drop, 3 clustering methods.
G. Lindgaard, and J. Chattratichart. CHI '07: Proceedings of the SIGCHI conference on Human factors in computing systems, page 1415--1424. New York, ACM, (2007)