Plugin to add and filter custom categories

Hi all,

I have a question about tagging posts with category names.

I am creating a blog where the posts should be categorized by City and by activity.

Ideally, I would like to modify the post form so that the user could choose from a list of cities (in a drop down box) and choose from a list of activities (in a drop down list).

Can you think of a plugin that will do this?

Thanks,

Jeff