I pronounce it like six-eighty-thirty, six-eighty-sixty...and 68000 being 68k, with the arch as m68k. I know, it's not even consistent.
And i say Ubuntu as "You-bun-too". But others say "Ooo-boon-too".
What about everyone else?
I had a boss back when Ubuntu was just getting some name recognition, and he couldn't remember what it was called. It came up in conversation and he referred to it as "Ubi Dubi." Since then that is what I call it :-) Interesting that everyone knows what I'm talking about even if they've not heard it before.