This article examines the nature and role of Web 2.0 resources and their impact on health information made available though the Internet. The transition of the Web from version one to Web 2.0 is described and the main features of the new Web examined. Two characteristic Web 2.0 resources are explored and the implications for the public and practitioners examined. First, what are known as 'user reviews' or 'user testimonials', which allow people to comment on the health services delivered to them, are described. Second, new mapping applications that take advantage of the interactive potential of Web 2.0 and provide tools to visualize complex data are examined. Following a discussion of the potential of Web 2.0, it is concluded that it offers considerable opportunities for disseminating health information and creating new sources of data, as well as generating new questions and dilemmas.