It seems that Steve Jobs attained a monopoly on the idea of being focused, as many of the articles I read lately on the subject refer to or quote him. Here's the latest one of them.
I might be breaking some unwritten law now, quoting someone else's take on what being focused means. I ran into this line in Ayn Rand's book The Art of Nonfiction:
When I was writing Atlas Shrugged, I accepted neither day nor evening appointments, with rare exceptions, for roughly thirteen years.
I like this example because not only does it demonstrate extreme focus, suitable for an extreme individual as Rand, but also discipline and persistency. These are complementary qualities without them focus is meaningless. Indeed, Rand's isolation wasn't in vain, as it allowed the creation of a book that became an instant bestseller.
Steve Jobs would have liked this example as well, as he himself may have been inspired by Atlas Shrugged when starting Apple...