I've been looking for an excuse to learn Java for years now and I finally found one. Over the weekend, my ISP was flaking out on me, so I decided to write an app to monitor how often my ISP forcefully disconnected my open TCP connections (which is really annoying for IRC usage). I initially wrote the app in C# as that is what I am more familiar with, then ported it to Java, using SWT for the UI.
As you can see, there is a defect in the Java version with the time counter, but otherwise it seems to work pretty well.
UPDATE: Wow, just tried to see how hard it would be to get the Java version running on linux and it turned out to be pretty easy! I am impressed!