One thing I found interesting in reading all the reports about the death of Rosa Parks is that she wasn't the first one to refuse to give up her seat on the bus.
At least three other people were arrested for refusing to give up their bus seats prior to the Parks incident; they live in near anonymity today. Parks went on to become an icon who received a host of awards, including the Presidential Medal of Freedom and the Congressional Gold Medal. Why her? What made her so special?
Very simply, Rosa Parks had greatness thrust upon her -- and she answered that call magnificently. She was not the first "Negro" to refuse to relinquish a seat in the "white" section of the bus, but she was among the very select few who had the courage to take a public stand against the prevailing institutionalized bigotry of that dark time.
History is full of people who helped change the world but are as unknown today as the three resisters who came before Parks. In all fairness, for example, Israel Bissell should be more famous than Paul Revere. Revere got captured before he finished the job. Bissell, whose unfortunate name doesn't rhyme with much, eluded capture and finished the job. And here's a whole list of heroes that history forgot. (Be sure to read the one about the Choctaw Nation.)
The fact that Parks wasn't first doesn't diminish her contribution; in fact, it enhances it. Rosa Parks didn't help change America by one act of defiance; most of us are capable of such momentary acts of bravery. It's what comes later, in the Oh-my-God-what-have-I-done? stage, where true courage can be found. She recognized that her act could become a powerful symbol, but only if she were willing to give up here life as she knew it by being at the center of a very long struggle.
UPDATE: Here's a longer, very thoughtful piece that explores the real story behind the "one woman in a single heroic act" myth.