I built a compiler that just threw out LLVM IR to stdout. Pretty great way to get something working, if you ask me, and lots of potential to do FFI or other kinds of integration. LLVM takes care of lots of portability issues, and optimizes your stuff.

My experimental stuff is here: https://github.com/djc/runa. The compiler is written in Python, and shouldn't be that hard to understand. I'm also happy to answer any questions about it here.