You've seen evidence of it all around the country: New York, Boston, L.A. Quietly, urban centers are making a comeback. But for a long time, little time or energy was devoted to inner cities. There was a kind of complacency, a feeling that poor neighborhoods were dysfunctional and there wasn't a whole lot anybody could do about it. But that's changing. And who is changing it? Well, some observers are crediting community development corporations, nonprofit businesses devoted to revitalizing housing and providing business opportunities in their neighborhoods, all owned and operated by residents of those impoverished neighborhoods.