Depends what kind of ideas you're looking for. I have followed the Parrot VM development for quite a while, though haven't had time to contribute a great deal to it due to Real Life constantly getting in the way.Any Ideas on ParrotVM ? http://parrotcode.org
Parrot has many features aimed at supporting dynamically typed languages, though that doesn't prevent it from running statically typed ones like JAVA (I recall someone developed a proof-of-concept JAVA bytecode to Parrot bytecode translator once). Parrot is a register based VM. It has GC (which is only conservative when it comes to walking the stack), a working JIT for quite a few platforms, NCI (so it can call into native code) and support for all kinds of other things that languages need to do (namespaces, objects, I/O, threads, aync I/O, events, MMD, continuations, etc). It builds on a wide range of platforms.
There's work to do yet, but Parrot is looking quite promising as a VM for running multiple languages and allowing interoperability between them (e.g. by allowing dynamically loadable oplibs, laying down some standard calling conventions, allowing different languages to express their own semantics with their base types while still allowing other languages to access them).
Jonathan
