Tagging solution or social bookmarks

Is anyone using a tagging solution or social bookmarks within vBulletin. I wish Crawlability would add a plug-in, as I'm very fond of their software.

This is in the works for the next version of vBSEO. If anyone has suggestions as far as specific implementation (location of the actual tags per threads, methods for allowing others to tag threads, strategies for increasing community collaboration in process, etc.), feel free to post here.

Remember, some of this new functionality (ping/trackback, tagging, etc.) has been historically more oriented towards tech communities. In forums, we need to take in consideration that many, MANY forums are not tech oriented, thus the challenge of making these features "non-tech user friendly" remains

Dropdown tag lists and tag clouds would be my preference.

What do you mean by "Dropdown tag lists"? Sample site?