building a search function

I need to build a search function similar to the one found on the front page at www.yelp.com.

Using this example, I need to have two boxes. In the first box, users will enter either the name or the type (category) of product they are looking for. In the second box, users will enter either a city state pair, or a zip code. The search will find either the name of the object in the location or a list of those types of objects in the location.

Any ideas about how to do this?

Thanks