From this site. There is a transcript of the segment as well.

Actually, Rabbi Heschel would have been 104 this month.  Back then, he absolutely got it - we cannot go forward unless we are together.

In 1965, Heschel wrote of his experience marching with Martin Luther King from Selma to Montgomery: "For many of us the march from Selma to Montgomery was about protest and prayer. Legs are not lips and walking is not kneeling. And yet our legs uttered songs. Even without words, our march was worship. I felt my legs were praying."

I have no doubt that if he were alive today, Heschel would be doing his best to continue in the path Dr. King had started upon.

Other remembrances of Dr. King: Audio and transcript of his 1967 speech on Vietnam at Riverside Church in NYC:

Over the past two years, as I have moved to break the betrayal of my own silences and to speak from the burnings of my own heart, as I have called for radical departures from the destruction of Vietnam, many persons have questioned me about the wisdom of my path. At the heart of their concerns this query has often loomed large and loud: "Why are you speaking about the war, Dr. King?" "Why are you joining the voices of dissent?" "Peace and civil rights don't mix," they say. "Aren't you hurting the cause of your people," they ask? And when I hear them, though I often understand the source of their concern, I am nevertheless greatly saddened, for such questions mean that the inquirers have not really known me, my commitment or my calling. Indeed, their questions suggest that they do not know the world in which they live.

Also, give the Rude Pundit a read, as well as Cliff.

Update, 1/18: Also check the yaller blogger's find on Dr. King's last social justice campaign - that of supporting the garbage workers' strike in Memphis.