The Scratch mod, Tiger
This mod of Scratch (scratch.mit.edu) will add several new features, including an extensive plugin API. It is currently developed by the Scratch user SJRCS_011.
Multi-platform execution environment for applications (and libraries) based on bytecode (compile once, run anywhere). Support for multi-language and multi-paradigm. It intends to be an open alternative to the Java and MS.NET platforms.
Lithium, the language independent scripting engine framework.
Troy is an independent, portable JVM implementation. The project aims at implemeting a virtual machine that is portable across many different platforms like Unix, Windows, Mac etc.