Unladen swallow: accelerating Python

I wouldn't call Unladen Swallow more ambitious than PyPy. PyPy's approach of allowing Python (or Python-like RPython code) to generate a pretty fast interpreter for any language is rather impressive. Even more so when you factor in that they now have a (prototype of a) JIT compiler that's generated for your interpreter and some extremely fast GC implementations (using which can perform better than C code on some benchmarks).