Don't know if you were able to catch Henry Louis Gates' Faces of America series on PBS a few months back, but it was an extremely interesting and moving program that traced the ancestry, as far back as possible, of a dozen prominent Americans.
Faces of America is also now a book, published by NY Press, "intended to be a tribute to the true triumph of American democracy, which is the diversity of our people, a diversity that we can now measure both through the branches of our family trees and in our genes."
Huffington Post recently posted an excerpt from Faces of America, looking at the unique family history of Olympic figure skater Kristi Yamaguchi: Faces of America: The Yamaguchi Story -- How an Immigrant Farmer Paved the Way for Success.