One of the favorite templates of SharePoint 2007 was the Site Directory. It allows users to tag their sites and make them searchable by their tags. A great template for your intranet. However, in SharePoint 2010 the Site Directory was not upgraded and is therefore not available when you try to create a site in the GUI.
Microsoft Consulting Services UK released a CodePlex version of the Site Directory which can be downloaded at http://spsitedirectory2010.codeplex.com/