The Thoughtfarmer team have published another excellent, practical intranet design article, this time on using online card sorting. It's a great complementary read to the other resources out there, not least my own thoughs on 'online vs offline card sorting'.
At its most fundemental level card sorting is about building an intranet navigation structure using terms and groupings that match users’ perspectives. The result is navigation that is easy to use. An effective card sort can help you find patterns and surface users’ mental models, the interpretation of which guides the intranet’s design.