Extensibility
TeamCity functionality can be extended in a number of ways. You can either make some declarative changes (using some bits of XML) which provide additional information about your builds, or you can write a real TeamCity plugin using the provided OpenAPI.
Third Party HTML Reports
If your reporting tool produces a report in HTML format, you can add a new tab to the Build Results page which will show the report.
External Status Widget
With a bit of HTML and CSS you can embed the status of your TeamCity builds to the home page of your site. You can choose a specific build configuration, and include or exclude a link to the build artifacts. The widget's look is fully customizable using CSS styles.
Displaying Custom Build Results
TeamCity has the ability to change the build status directly from the build script. You can set the status (build failure or success) and change the build description text.
Declarative statistical charts and custom metrics
You can create your own statistical graphs. Just provide the required data in the XML configuration files. No additional TeamCity plugins need to be developed.
Plugin Development
Using TeamCity's Open API you can provide integration with different change management systems, build tools, IDEs, and notification means.
Become a member of TeamCity plugin development community and access more information in the plugin development space.