Grid resources are distributed on the Internet. It is important to establish diverse virtual organizations with special sharing policies. The spaces model has the advantage in coordinating different applications on grids. We propose a spaces based model to share and use resources in virtual organizations. A virtual organization is set up as a resource tree, in which spaces act as trade platforms for resource consumers and providers. Resources are aggregated into multiple spaces that cooperate in completing a complicated task. Virtual organizations are coordinated through a virtual space grouped by some spaces. The above ideas thus offer a promising route for organizing heterogeneous distributed resources in a simple way.