In this paper, we study the power allocation problem at the relay nodes for two-hop F/TDMA networks with multiple sources and destinations. Each relay node is assumed to be capable of assisting multiple source nodes and of selecting one of regenerative decode-and-forward (RDF), nonregenerative decode-and-forward (NDF), amplify-and-forward (AF) and compress-and-forward (CF) relaying strategies to assist each source node. Considering the sum capacity as the performance metric, we solve the problem of optimally allocating the total power of each relay node between the transmissions it is assisting. We first obtain the optimum power allocation policies for the relay nodes when the relaying strategies of all source nodes are given. Next, to obtain higher sum capacities, we investigate the optimum power allocation problem jointly with relaying strategy selection. We observe that optimum power allocation with the appropriate hybrid relaying strategies provides higher sum capacity than pure RDF, NDF, AF or CF relaying strategies.