The Seattle Times has a great site devoted to MLK Jr.
Coretta Scott King on the meaning of MLK Day:
It is a day of interracial and intercultural cooperation and sharing. No other day of the year brings so many peoples from different cultural backgrounds together in such a vibrant spirit of brother and sisterhood. Whether you are African-American, Hispanic or Native American, whether you are Caucasian or Asian-American, you are part of the great dream Martin Luther King, Jr. had for America. This is not a black holiday; it is a peoples' holiday. And it is the young people of all races and religions who hold the keys to the fulfillment of his dream.
From his final speech, given the day before he was murdered:
Well, I don't know what will happen now; we've got some difficult days ahead. But it really doesn't matter with me now, because I've been to the mountaintop. And I don't mind. Like anybody, I would like to live a long life - longevity has its place. But I'm not concerned about that now. I just want to do God's will. And he's allowed me to go up to the mountain. And I've looked over, and I've seen the Promised Land. I may not get there with you. But I want you to know tonight, that we, as a people, will get to the Promised Land. And I'm so happy tonight; I'm not worried about anything; I'm not fearing any man. Mine eyes have seen the glory of the coming of the Lord.