mzscheme has a rather good C API. I was thinking about using it to generate C code for Arco that would less rely on mzscheme after each release, before both are totally independant.
I am currently working on the one at the first address. I translated it to Arc. In other words, I have a scheme compiler written in Arc that can hardly do anything but compile the fib function to C.
Pretty soon, I'll have something compiling a poor subset of Arc (only fixnums and symbols, no list, no bignum, no GC, no special syntax, but with closures and call/cc fully operational).
