If you run FogBugz on your own server, you can use Plugins to customize it to meet your unique requirements. Plugins can add new features, modify existing functionality, and make FogBugz integrate with other applications.
Extras and Add-Ons
In addition to the Plugin API, the FogBugz XML API allows any web-enabled application to communicate with a FogBugz site.
The Extras page lists all of the offerings from Fog Creek Software and third-party vendors that use the FogBugz XML API.
Automatically Documents Intelligent Screenshots of a Defect with Seamless Submission to FogBugz
While editing a case, allows a user to schedule a reminder notification or other future event.
Add UML, Flowcharts, Wireframes / UI Mockups, Mindmaps and more to Wikis and Cases
Provides extended reports from the WorkingOn timesheet information
FNN - FogBugz News Network (Extended Reporting)