Wireless mesh networks can increase wireless connectivity by routing packets through multiple wireless hops. However, a very efficient wireless interconnection is necessary to make these networks operative in practice. In this paper we describe a technique to increase the throughput of wireless mesh networks, based on cooperative communications. In the proposed setup, multiple nodes cooperate at the physical layer by jointly transmitting or receiving data. In particular, two cooperative strategies are proposed: opportunistic relaying, and partial decoding. In order to integrate such transmission scheme in a mesh network, each cooperative set of nodes is organized in a unit called virtual link. Virtual links can be seen by the network layer as regular links, which hides the cooperative strategy from the routing algorithm. Simulation results for Rayleigh and Rice fading show remarkable gains of the cooperative strategies with respect to non-cooperative transmission.