Modules are extensions to Drupal sites which enable extra functionality. Some things just can't be done via configuration and must be done in a module.
Our team has created or contributed to many of the most popular modules in Drupal. For a partial list please see Greg's list of modules he developed or maintains and Ezra's drupal.org profile page.
If you need a module developed for your site, please contact me with the details of what features you need. Often we are able to user our site-architecture skills to leverage existing community modules for much of the functionality to give you a great solution at a reduced cost.
