A Java 2 (JDK 1.3/1.4) compatible virtual machine. joeq is unique in that it is almost entirely implemented in Java, making it reliable and efficient. It is also language-independent, so code from any language can be seamlessly and dynamically compiled.
several vaguely related projects worked on by me: a 3d engine with a javascript-like scripting language (pdsys); an older scheme dialect (vmsys); ... (2009-04-28: I have been gone for years, may try to put up some newer stuff...).