Scheme to C in 90 Minutes
The Montreal Scheme/Lisp User Group site has an archive of a presentation given at one of their meetings in which a simple Scheme to C compiler was constructed. It doesn't support the whole Scheme standard, but does support optimized tail calls, continuations, and full closures.
90 minutes is pretty good for a language compiler, even if it doesn't compile to native code! Scheme is a great language for studying compilation techniques since it's so easy to transform.