This old Georgia Tech visualization paper looks worth a read, especially given the boom in online audio and video:
We present a new user interface technique for the visualization and playback of long media streams decorated with significant events. Our Multi-Scale Timeline Slider allows users to precisely focus on a specific location in a very long media stream or set of streams based on significant events while also retaining the stream's entire context. KEYWORDS: Timeline slider control, multimedia streams, visualization, focus + context.
Authors: Heather A. Richter, Jason A. Brotherton, Gregory D. Abowd, Khai N. Truong
Via TomC's linklist