http://chrisseaton.com/rubytruffle/cext/
Has anyone in the Python community thought of doing something similar, e.g. using PyPy to build a C interpreter, maybe re-using front-end components (pre-processor, parser, type-checker, etc.) from an existing C compiler? In fact, it might be useful to build an interpreter for something like LLVM IR, or even x86 machine code, in order to gain access to a bunch of existing languages.
Once access is gained at that low (ABI?) level, abstractions and interfaces can be built to hide the horribleness. The performance would initially be terrible, but some targetted, profiling-guided optimisation might get it down to reasonable levels; in a similar way to a JS interpreter adding specific optimisations to make asm.js code run fast.