I've been playing around with some Java programming using Sun's NetBeans 5.5 IDE, primarily for the Matisse GUI builder. As a programming exercise, I reimplemented a little Unit conversion calculator (things like inches to feet as well as a lot more exotic stuff) that I originally wrote and sold as a Windows shareware application way back when. Unfortunately, that app used some old Win16 libraries so it was sort of broken on current systems.
In any case, this new app largely recreates the previous version's function (including the ability to customize the unit database and add information about the units which the program will display). It's written in Java, so it should run on anything with reasonable graphics that has J2SE 5.0 or later installed. I've tested it on Windows XP and SUSE LINUX 10. It could still stand some polishing; e.g. it doesn't have an installer. But it appears to basically work. You can download it here: jconvert02.zip.