Recent works have proposed a number of models and tools to address the growing needs and expectations in the field of e-Science. At the same time, the availability and models of use of networked computing resources needed by e-Science are rapidly changing and see the coexistence of many disparate paradigms: high performance computing, grid and recently cloud, which brings very promising expectations due to its high flexibility. In this paper we suggest a model to promote the convergence and the integration of different computing paradigms and infrastructures for the dynamic on-demand provisioning of the resources needed by e-Science environments, leveraging the Service-Oriented Architecture model. In addition, its design aims at endorsing a flexible, modular, workflow-based collaborative environment for e-Science. A working implementation used to validate the proposed approach is described together with some performance tests.