Q:

Sharepoint tagging like serverfault?

Does a Sharepoint plug-in / add-in exist that will support serverfault-style tagging for documents?
Key features:

Users can add their own tags just by typing them
Autocompletion whilst typing shows the user what tags already exist

A:

One thing to take into consideration is how these things will upgrade to the next version of SharePoint. Is the data stored in a list or a custom database?
The Office server team bought a company a couple years ago that specialized in metadata and taxonomy management that was to be integrated into future products. Hopefully we'll know more at the SharePoint Conference coming in November.
In the meantime, you might want to check out the Podcasting Kit for SharePoint. They have some tagging features that they built out and there is a good chance that team will have some migration to SharePoint 2010. Would love to see someone on the team confirm or deny what their plans around 2010 is.

A:

Yes.  A search on Codeplex.com for "tag cloud sharepoint" reveals a variety of choices.  I have never used any but the site has rankings, reviews, and comments that can help you narrow down your options.

