I'd be mixed on the Darwin day. I can't say that a scientist who has influenced all of us so much shouldn't get a day, even if he wasn't American, but I don't think we need one more day. It would just be one more day off for bankers.
And I loved Kary Mullis' book, but I couldn't recommend a day for him, either. It did remind me of a thread I wanted to start, though, so...off to start it.