This volume of Lecture Notes in Computer Science contains all accepted papers th of the 5 International Conference on Innovative Internet Community Systems 2 (I CS), which was held at the Sorbonne in Paris, from June 20–22, 2005. The previous four conferences in Ilmenau, Rosk, Leipzig (Germany) and Guadalajara (Mexico) developed the profile of this event. Traditionally, there are topics discussed in three main aspects. All of them must be considered in a united manner in order to investigate and understand the emergence and evolution of communities in the Internet: knowledge about networking, content and text processing as well as theory. The goal of the I2CS workshop is to bring researchers from both industry and academic fields together to discuss current progressandfuturedevelopmentsintheseareasandtoeliminatethegapbetween theory and application. At this point, we want to express immense gratitude to all the authors of the submitted papers and to the members of the international Program Committee for their contribution to the success of the event and a program of high quality. In a peer-to-peer review process, 17 papers were selected out of 27 submissions.