[Plugin idea: Automatically linking tags appearing in posts]

I was wondering if anyone knew of any plugins out there that do this currently or any thoughts as to the feasibility of creating a plugin to accomplish the following functionality:

I want to create “Topics” pages on my blog similar to what the New York Times does. I certainly don’t expect functionality as rich as theirs, which I imagine was fully built and customized in-house.

My thought for doing this is to make tags that appear in my posts to automatically be linked to the tag page for that post (i.e. if “Barack Obama” appears in my post, then his name would link to /tag/barack-obama/ on my site.

Since in order to do this, one would need to hook into the_content to add the links before displaying a post, I think it would probably be best to only scan for the more popular tags–those that are in more than X articles (X of course is variable). The more popular tags I think would need to be generated on a semi-regular basis, NOT with every pageload. Perhaps by some sort of Cron job can handle this? I don’t know how this works in WordPress, to be honest.

Does something like this exist already for making topics pages? If not, does my idea for how to do this seem reasonable and possible to implement? Do you have any other ideas?

Thanks!

-Scott