The MIT Technology Review just published a large article on the Semantic Web and Web 3.0, in which Radar Networks, Metaweb, Joost, RealTravel and other ventures are profiled.
Social tagging: Artificial Intelligence > Collaboration Tools > Collective Intelligence > Groupware > Knowledge Management > Radar Networks > Search > Semantic Web > The Future > The Metaweb > Venture Capital > Web 2.0 > Web 3.0