Perhaps I'm obsessing over this whole user-generated content phenomenon—and I don't want to overhype it. But in my view, this is one of the most interesting things happening online. I tried to capture the phenomenon in the context of Yahoo!'s local strategy previously.
This piece in BusinessWeek is a very interesting survey of the different applications and companies that are leveraging community and user-generated content (broadly defined) to create a "next-generation" set of tools and services online.
Worth the few minutes to take a look.