"What" and "Where" forms inside the Search form.

I'm sketching a web-app, like a standard YellowPages. At the top I want to place an autocompletable dual search box, like we see on most YellowPages sites:
What? (Taxonomy, Product name, Username) AND Where? (Location).

I'm interested to see what the members of this group have found to be best modules to achieve this type of standard YellowPages functionality???

How can you have 2 boxes inside the search form, one of which is a Location search box?

This type of dual-box search is pretty standard for Directories,so I'm wondering how it can be best achieved in Drupal?