The rapid proliferation of Online Social Networking (OSN) sites, like Facebook and MySpace, is expected to reshape the Internet’s structure, design, and utility. Industry experts believe that OSNs create a potentially transformational change in consumer behavior and will bring a far-reaching impact on traditional industries of content, media, and communications. Nevertheless, at a European level, there is a recognized shortage of highly skilled researchers, scientists and engineers trained in building IT platforms and service infrastructures capable of hosting innovative OSN services and applications. The iSocial consortium, which consists of 7 full partners and 6 associate partners, envisions the emergence of distributed and scalable overlay networking and distributed storage infrastructures that will provide support for open social networks and for innovative social network applications, preserving end-user privacy and information ownership. The main objective of iSocial is to provide world class training for a next generation of researchers, computer scientists, and Web engineers, emphasizing on a strong combination of advanced understanding in both theoretical and experimental approaches, methodologies and tools that are required to develop Decentralized Online Social Networking platforms. iSocial training network will fund 11 Ph.D. students; 5 post-doctoral fellows for 18 month stays, 2 intensive post-graduate schools, 3 workshops and a final Conference. To meet this goal, iSocial is divided into four interconnected research topics: i)Overlay Infrastructure for Decentralized Online Social Networking Services; ii)Data storage & distribution; iii)Security, privacy & trust,iv) Modelling and Simulation. These topics include important and timely research challenges with a high exploitation potential.