card sorting application
Screenshot: ipragma.com
"xSort is a card sorting application for Mac OS X. It allows you to easily define a new card sorting problem, perform several sessions with multiple participants, and finally analyze the results (using multiple criteria) and generate printable reports.
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Card Sorting is a technique for exploring how people group items, so that you can develop structures that maximize the probability of users being able to find items. (in Card Sorting (Design Usability Resources) - Information & Design). This technique is often used in the construction of web sites."