This article came out while I was gone. The author offers a detailed overview of Web 2.0 and examines some of the implications for learning. I think the emphasis on search is a bit misplaced, but the article still captures the essence of web 2.0, pointing out, for example, that it allows people to create their own content and to use several distributed services simultaneously. The impact on education is discussed near the end of the article, but is cautious in tone: "The story of this wave of innovation, whether we call it Web 2.0 or something else, is itself emergent and uncertain." Related: List of Web 2.0 applications.