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...).
JLog is a Prolog interpreter written in Java. It is fast and perfectly suited for education. It includes source editor, query panels, online help, animation primitives, and a GUI debugger. JScriptLog is Prolog in JavaScript.