Most current cloud provisioning involves a data center model, in which clusters of machines are dedicated to running cloud infrastructure software. Ad-hoc mobile clouds, in which infrastructure software is distributed over resources harvested from machines already existed and used for other purposes, are gaining popularity. In this paper, a trust management system (TMC) for mobile ad-hoc clouds is proposed. This system considers availability, neighbors' evaluation and response quality and task completeness in calculating the trust value for a node. The trust management system is built over PlanetCloud which introduced the term of ubiquitous computing. EigenTrust algorithm is used to calculate the reputation trust value for nodes. Finally, performance tests were executed to prove the efficiency of the proposed TMC in term of execution time, and detecting node behavior.