Synchronization in chaotic oscillatory systems has a wide array of applications in biology, physics, and communications systems. Over the past 10 years there has been considerable interest in the synchronization properties of small-world and scale-free networks. In this paper, we define the fitness of a configuration of coupled oscillators as its ability to synchronize, which is related to the ratio of the largest and smallest eigenvalues of the coupling matrix. After an analysis of the fitness landscape of the coupled oscillators problem, we employ an optimization algorithm to determine network structures that lead to an enhanced ability to synchronize. The optimized networks generally have low clustering, small diameters, short path-length, are disassortative, and have a high degree of homogeneity in their degree and load distributions.