Use a third-party CSS or JS Framework, a self-hosted service like a CRM, or a third-party service with the site.
Existing code of the Count Nodes project. (http://drupal.org/project/count)
This module provides a block which contains a form that allows users to login to a WHMCS script.
This module provides API integration with the Go Daddy Reseller API so that domains can be registered and managed through your Drupal site.
Integrate with the oboe logging infrastructure developed by Tracelytics to log specific information about Drupal execution.
This is a simple module for integrating with Protonotes which can often be useful for getting feedback on a site during prototyping.
A similar module is [sticky_notes]
This module allows you to receive Ubercart payments via the Flo2Cash Web2Pay payment gateway.