This book constitutes the thoroughly refereed post-conference proceedings of the Third International Conference on Digital Eco-Systems, OPAALS 2010, held in Aracaj?, Sergipe, Brazil in March 2010. The papers cover topics from Social Science, Computer Science and from Natural Science. These include social networks, social technologies, digital ecosystems, knowledge management, context-aware situation and digital ecosystems, Lie group analysis, constructive dynamical spaces, and interaction computing.