Pyston is a new, under-development Python implementation built using LLVM and modern JIT techniques with the goal of achieving good performance.
Emscripten is an LLVM-to-JavaScript compiler. It takes LLVM bitcode (which can be generated from C/C++, using llvm-gcc or clang, or any other language that can be converted into LLVM) and compiles that into JavaScript, which can be run on the web (or anywhere else JavaScript can run).
The LLVM Compiler System. Chris Lattner.
