The Diligent project (A DIgital Library Infrastructure on Grid ENabled Technology) launched in September 2004, is a joint effort by thirteen European research and industrial institutions. By combining Digital Library and Grid technologies, the project has developed an e-Infrastructure that supports the sharing of content resources, application services that manipulate these content resources to produce new knowledge, and computational resources, which physically store the content and support the processing of the services. By relying on the sharing of these resources, the e-Infrastructure also offers functionality for creating and maintaining Virtual Research Environments(VREs), i.e. collaborative digital environments through which scientists, addressing common research challenges, exchange information and produce new knowledge. The core technology supporting such thee dimensional e-Infrastructure is a service-oriented application framework named gCube (http://www.gcube-system.org)/. The DILIGENT e-Infrastructure currently supports two VREs, responding to the needs of very different class of scientific communities: ImpECt serving the Environmental Community in the generation, periodic maintenance and publishing (through ad-hoc on-demand processing) of environmental reports, and ARTE, supporting researchers in the humanities in creating e-courses through the exploitation of advanced analysis functionality on multimedia material. Additional VREs, serving other scientific communities, are under construction.