This book constitutes the thoroughly refereed joint post-proceedings of the three International Workshops on Grid Middleware, CoreGrid 2006, the UNICORE Summit 2006, and the Workshop on Petascale Computational Biology and Bioinformatics, held in Dresden, Germany, in August/September 2006, in conjunction with Euro-Par 2006, the 12th International Conference on Parallel Computing. The 29 revised full papers presented were carefully reviewed and selected from a total of 50 submissions. The 16 papers presented at the CoreGRID Workshop on Grid Middleware focused on knowledge and data management on grids, grid resource management and scheduling, as well as grid information, resource and workflow monitoring services. The 8 papers presented at the UNICORE Summit 2006 show current developments and implementations of the UNICORE middleware system, which today is used in daily production worldwide. Beyond this production usage, the UNICORE technology serves as a solid basis in many European and International projects. The concern of the 5 papers of the Petascale Computational Biology and Bioinformatics Workshop was to show what bioinformatics or computational biology applications can or should accomplish with petascale computing environments, and what obstacles must be overcome in order to implement and use effective and important problems in the life sciences (biology, biochemistry, environmental sciences, etc.).