If you have written a servlet or a single JSP, it is almost guaranteed that you have used Apache's Tomcat Server. Whether you use it for development, to run intranet applications, or to serve your production needs... Tomcat is ready and willing to step up to the plate.
There are many different ways to manage your Tomcat instance, but for a great "Web 2.0" interface with lots of bells and whistles, take a look at Tomcat Probe.
Tomcat Probe is the ultimate tool to manage and monitor your Tomcat instance. Lightweight web user interface, killer features, no-fuss installation and weekly updates. Tomcat Probe gives you total control over live Tomcat instances and applications.
The interface provides for the management of deployed webapps, JSP's within apps, and data sources. You can view all kinds of stats for threads, charts for traffic information, download log files, call the garbage collector and much more. All of this with a great looking interface.
Even if you don't have a need to use this tool, it is worth a look.