Fythe is an in-development VM for dynamic languages. Its initial target is Plof, but it's designed to be general-purpose. It accomplishes this by exposing low-level constructs, but limited just enough to allow fast GC and tables. The (incomplete) spec is available at http://fythe.org/fythe.pdf, or in HTML at http://fythe.org/spec/. There are implementations in JavaScript and C. The JavaScript version can be accessed online at http://fythe.org/demo/jsfythe.html, but that interface is mostly undocumented. Both are released under the MIT/X11 license, and available via Mercurial at https://bitbucket.org/GregorR/fythe/. The spec's LaTeX source is also available via Mercurial at https://codu.org/projects/fythe/spechg/.