On line web directories can serve a beautiful dual purpose for both the businesses listed and the customer.

Initially as many people come to a well made and sensibly structured directory such as the dMOZ they will be able to browse down through categories and refine their search until they land on a page with just what they are looking for.
It can be so much better than using a search engine as with each step you refine your selection.

On the other hand a business owner knows this and will surely want the customer to find them. The customers who eventually land on their site by means of such a business directory will, naturally, be good customers who, rather than randomly dropping in will actually have a real and targetted interest in the site’s products or services.
A further advantage to the business owner is that some search engines base their ranking upon inbound links from trustworthy sources, so a link from a bona fide directory will enhance the website in search engine optimisation terms also.

Directories will contain many useful subcategories such as at the Finance Section of the DMOZ, where one is able to see purely Finance Related Links.