Filtered Table of Contents

Just learning SharePoint 2010, so sorry if this is simple. Is it possible to filter a Table of Contents web part so it shows only sites meeting certain criteria? Ideally I'd like to add tags to the sub-sites, and then filter the ToC based on these tags. However, I don't know if tags even exist in SharePoint 2010 and I can't figure out how to filter a ToC. Any thoughts would be appreciated.

Thanks!