A scientific growth area in recent years has been the study of networks of interacting entities within a population, including species in food webs, human or other animals transmitting infection, proteins in cells, cells in organisms (e.g. neuronal networks), the internet and the World Wide Web. Here, I review some of the differing network patterns that arise in theory and in practice, with an emphasis on their dynamical implications, particularly for resistance to deliberate or accidental disturbance. I offer caveats and opinionated comment about some excesses of enthusiasm and suggest some areas where these network ideas might find further application.