This article in Smashing Magazine lists 31 examples of innovative data visualization. The list includes well known "classics" such as newsmap, digg stack,  flickrtime, Hans Roslings TED talk, and musicmap, but also many others you might not have seen. They are presented in the following categories: Mindmaps, Displaying News, Displaying Data, Displaying Connections, Displaying Websites. This is a really good source of inspiration, and to help carry you from inspiration to creating your own visualizations, the article also provides annotated links to helpul Articles and Resources, and Tools and Services.

Note: see also the Periodic Table of Data Visualizations and Places & Spaces: Mapping Science