Against the idea of a business directory module

We built a business directory using Drupal 6 with Solr 3.4 integration. See http://www.webnetwork.com.au

I personally am against building a "business directory" module as I see it would be limiting. Business directory websites can vary so greatly in features so it would be much better to use configurations of different Drupal modules to create a specific set of features rather than a business directory module per se.

In our directory, some of the core modules we used:

Apache Solr
Solr Location
content profile integration extending user profiles
custom content types with various CCK datatype formats for custom fields
Invitations
page title
auto alias
roles and permissions
views
blocks
taxonomies

The Solution

The directory search offers both keyword / keyphrase search integrated with faceted drill-down, and the facets are controlled through taxonomies. Some facets use a locked-down single taxonomy selection, and others offer the user multi-value free autocomplete tags enabling users to enter their own taxonomies at registration.

Controlling the bias settings on the Solr search node with faceted control of search have made search results very reliable in the site. The keyword / phrase "did you mean" suggestions add even more dimension to the users search experience.

The use of Page Title and setting automatic alias patterns has enabled good indexing of directory content in search engines also.
Issues

We did find that the Apache Solr 3.4 location module (used to capture gelocation data of businesses and hook dynamically into Google Maps) initially needed some customisations to get working with search.

One draw back we found was that the data fields in Solr Location module (suburb, postcode / zip or state) are not facetable meaning users cannot drill down by these fields.

See the directory here: WebNetwork.com.au