The (partly) Karlsruher project "Semantic Wikipedia" deserves a lot more publicity then it's getting. It is a well thought out plan to extend wikipedia in the direction of the Semantic Web.
From Dennys Blog:
[...] we propose the introduction of typed links as an extremely simple and unintrusive way for rendering large parts of Wikipedia machine readable. We provide a detailed plan on how to achieve this goal in a way that hardly impacts usability and performance, propose an implementation plan, and discuss possible difficulties on Wikipedia's way to the semantic future of the World Wide Web. The possible gains of this endeavor are huge; we sketch them by considering some immediate applications that semantic technologies can provide to enhance browsing, searching, and editing Wikipedia.