In this paper, we consider simultaneous transmission of information and energy in a wireless network with channels undergoing frequency-selective fading. The receivers are capable of decoding the information as well as harvesting energy from the same received signal. The network employs orthogonal frequency division multiplexing (OFDM) for signal transmission. In this context, we address two different problems and propose suitable algorithms for transmit and receive processing. The first problem is the optimal resource allocation for maximizing weighted sum-rate of the users while guaranteeing a minimum harvested energy at each receiver. In order to achieve this target, we propose an iterative algorithm that allocates a set of subcarriers to each user, allocates power to each subcarrier, and computes the optimal ratio of the received signal power that goes to the information decoder and the energy harvester. The second problem is the optimal resource allocation for maximizing the total harvested energy under constraints on the minimum rate achieved by each user. We propose resource allocation and receive processing algorithms as in the previous case. Numerical results are provided, and the merits of the proposed design for various operating conditions and parameters are illustrated.