News, discussion, and opinions travel through an overlapping set of on-line networks, involving e-mail, blogging, and other forms of communication. We discuss a set of approaches for tracking pieces of text as they travel and mutate in these networks, applying these ideas to a set of related problems. First, we show how this type of analysis can capture temporal patterns in the news over a daily time-scale --- in particular, the succession of story lines that evolve, compete for attention, and collectively produces an effect that commentators refer to as the 'news cycle.' Second, we show how this approach can be combined with an analysis of network structure to trace the diffusion of specific pieces of information as they spread between people at a global scale. This talk includes joint work with Lars Backstrom, Jure Leskovec, and David Liben-Nowell.