What other languages can produce byte codes that can be used by the Java Virtual Machine?

Practically every language from C++ to Visual Basic can be converted in some form to Java byte codes. The converted program may not benefit from designing a program with object-oriented principles, but you won't have to learn a new language to do it. For a current list of available language support, see http://grunge.cs.tu-berlin.de/~tolk/vmlanguages.html.