I was surprised to see Mike Blair at the Lisp conference. Mike is an old friend of mine and we've worked on several projects together. He's very sharp and has some fantastic ideas about dynamic program optimization (examining the statistics of runtime values to guide JIT compilation).
Mike knows computing from the transistor on up through the
meta-circular evaluator. (And even the meta-meta-circuluar. I recall
that he once got the meta-circular evaluator to run itself. It took
about forty minutes to get to the prompt.) I've seen him program a
micro-coded Turing machine and I've worked with him on a spreadsheet
program. He was at Transmeta for some time and has some interesting
stories about debugging Microsoft Windows from below (finding bugs
where Windows unintentionally relied on hardware behavior that was
known to be probabilistic).