Hi, I’m Adri Verlaan, a developer on the ECM team. I would like to introduce you to a starter kit that I’ve developed for SharePoint Server 2007 that helps with the implementation of a taxonomy/tagging system. The kit contains a lightweight working prototype, which you can extend to create a solution that will meet your needs.
Currently, the kit allows authors to attach tags to content and readers to specify tags in which they are interested. Using this information for a specified content source, a customized Content Query Web Part shows only the items that match a reader’s respective tags.
Here's a screenshot of the Property panel for an item (in this case, it's the "Interesting Page" page) that has been extended with a couple of taxonomy columns ("Vehical Type" and "Drive Train") for which content authors can select specific keywords.
For more information and the downloadable file for Taxonomy/Tagging Starter Kit for SharePoint Server, go to http://www.codeplex.com/CKS/Release/ProjectReleases.aspx?ReleaseId=2830.