Following on Sandra's comment, I've heard "half-caste" quite often in the UK, Australia and New Zealand. I assume it's a relic of the Empire, i.e. from India. It was almost invariably derogatory - in New Zealand the implication was that such people didn't even have the perceived redeeming value of "pure-blooded" Maori, being mostly urbanized proletarians with no traditions of deference. There was a whole raft of ugly stereotypes about being mixed-race in NZ, though when they got politicized it was more in the direction of European fascism than the American slave-society model.

I never did figure out *why* "Negro" became perceived as an insult. On arriving in the US from New Zealand in 1974, I used it when talking to my Afro-American neighbour and he looked at me as if I'd just been chipped out of a dinosaur fossil deposit. I got his point, but it had never occurred to me that the word itself could carry any negative connotations, any more than "Maori" did; in fact, to this day I don't think I've ever heard it used as a derogatory term.