post tagged by reader

Hi Guys,

I am developing a new project on which the actual readers can tag a specific post that I create. However, they can only pick tags from a list that is already available (created by the admins).

After that, I want to show a series of stats, like the most used tag, etc.

Is there a plugin that can sort this out? How do you suggest I deal with this situation?

Thanks in advance!
Rui