Cloud computing is a technology of enormous scope for innovation especially in a volatile market and rapidly evolving, in which, the ability to exploit new technologies and remaining competitive is more important. However the choice of Cloud providers, whose offers best fit the requirements of a particular application, is a complex issue due to the variety of potential options and the number of variables to consider. In this paper we propose a distributed cloud broker that have the main task of selecting dynamically a set of Cloud resources, from different vendors, that best fits users requirements. Brokering has been developed as a service over the Cloud to exploit the elasticity of such compute utility and to provide scalability respect to a dynamic changing workload.