If you are a SharePoint 2007 shop or thinking about becoming one check out this article on how a Microsoft Partner called Provoke built a custom metadata repository and surfaced it up through SharePoint. I see this method being a trend for enterprises as we start to mature in the practice of information architecture.
The process for the information architecture design took place within two weeks in what would normally take place over several months. Therefore, a lot of the IA work was based on assumptions, and the tag driven system we created allows flexibility for future iterations. Expertise in information architecture accelerated the process a bit.
Using well known and heavily used consumer blogging methods such as tagging added to the usability of the system. This combined with metadata makes the system usable and extensible so that surfacing information is more meaningful to the context of the user.