For a few years, social software has appeared on the Internet to challenge the problem of handling the mass of information available. In this chapter, we present the GALILEI platform using social browsing to build communities of interests where relevant information and expertise are shared. The users are described in terms of profiles, with each profile corresponding to one specific area of interest. While browsing, users’ profiles are computed on the basis of both the content of the consulted documents and the relevance assessments from the profiles. These profiles are then grouped into communities, which allows documents of interest to be shared among members of a same community and experts to be identified.