This paper considers a particular case of virtual organization composed of the following entities: institutions, online laboratories wishing to collaborate to share hardware and software resources. In the literature, cloud computing represents an implementation of the virtual organizations as grid computing. However, the benefits of the cloud are not used to the full in virtual organizations. This paper shows that it is possible to form a virtual organization around an IaaS cloud to enable member organizations of virtual organization to obtain supplies of resources on demand. Scarce resources shared by member organizations are also in the cloud. For this, we proposed two models of sharing resources: the centralized model for resources accessible via web and the decentralized model for physical resources not accessible via web. We used OpenStack platform to implement our solution.