Best way to enable sorting by 3 criteria on a page of listings

Question

If you go to this site: http://www.ec-ohio.com and click on one of the links in the Directory (left column of homepage) you generate a page with listings, and at the top of each page there's 3 links that let you sort the page content by city, county or product.

I want to rebuild the site in WP, but am wondering how to enable that kind of sorting. I was going to enter the listings via custom post types.

Any advice greatly appreciated!