Taggem is a web-based contact management system built in the early days of PHP app popularity. It utilized AJAX interactions and layout templates before jQuery and Smarty existed. Released in 2005, it is still in production use handling 100,000 contacts for the small government contractor Dawnbreaker, Inc.
Before Taggem, Dawnbreaker used Filemaker Pro to manage their contacts. Lacking in many features, especially multi-user capabilities, I was asked to create a web app to replace it. The system was designed with flexibility in mind. The web UI allows adminsitrators to change contact schema without knowing SQL and change layouts without knowing much HTML. Advanced search forms allow fuzzy or exact matching and a robust tagging system provides a means to notate each contact based on granular access control. The original system also included a mass mailing feature, but that was discontinued as superior third party offerings became available.
PHP, MySQL, AJAX (pre-jQuery)