I'm thinking about buying "Microtrends: The Small Forces Behind Tomorrow's Big Changes by Marc Penn." Here's an overview of it from Microtrending.com:
Penn and his co-author E. Kinney Zalesne argue that the biggest trends in America are the microtrends -- the smaller trends that go unnoticed or even ignored. One percent of the nation, or 3 million people, can create new markets for a business, spark a social movement, or produce political change.
The book covers a variety of topics from politics to leisure and relationships. I think that although the book isn't directly geared towards designers, it seems like it would have great relevance to developing marketing or advertising strategies. I think that the old approach of targeting the masses is fading while marketing to smaller niches is more relevant in today's more individualized culture and society.