Via Mark, I ran into RAPID for SharePoint, a tool to add taxonomies functionality to SharePoint 2007. We've been talking about this kind of feature a lot here and implemented in some 2003 project already. RAPID has made a great implementation for 2007 which is certainly worth while looking at!
"'RAPID for SharePoint' builds upon the success of it's predecessor (CMS.RAPID) by providing a comprehesive classification solution for Microsoft Office SharePoint Server 2007. As well as providing this significant new functionality to the product 'RAPID for SharePoint' also features a number of useful editing, administration and useability enhancements for SharePoint 2007.
The 'RAPID for SharePoint' Classification system will be available in a range of versions towards the end of March 2007. It enables SharePoint 2007 to meet current Public Sector compliance requirements by supporting a range of Taxonomies including IPSV."