This secured Mount Vernon site is used by all employees to retrieve payroll information, W-2s, 401K, insurance and withholding elections. They can also request changes to their employee information, insurance, withholding, etc.
This is an older Drupal site, but it features quite a bit of integration with Mount Vernon's back office system, running on an iSeries (aka AS/400). The backend software is written in SQLRPGLE. The access from the Drupal modules (PHP) is via direct connection to the iSeries database via ODBC, and by calling stored procedures. The Drupal front-end handles the user security, presents the information, and collects input via WebForm.
I also wrote a module to add/remove users from the Drupal site to sync with changes in the backend database.