Mnemograph: Web Based Timeline Software
Free tool to create online Flash-based interactive timelines.
Dipity
Create a timeline by adding each event manually or by adding a source (Flickr, RSS, twitter, etc.) Images, music, and video can be included in events. Related services include Tickr, which lets you create a dynamic timeline with Flickr images based on search criteria, and TimeTube, which does the same for YouTube. Some people are playing with this as a way to visualize the river of information from the Connectivism course (CCK08) this fall.