I was looking for good javascript frameworks that do data visualization. I found couple really good ones: Raphael + g.Raphael, D3, and processing-js. But what really strikes me that we don't have a good idea how to visualize flow of Time and Data. An example of such flow diagram was published by google:
http://analytics.blogspot.com/2011/10/introducing-flow-visualization.html
But I haven't seen any other project that would propose a flow visualization that would be as clear and uncluttered as google analytics is.
EDIT: the graph is called "alluvial diagrams" - but I'm still hungry for more (thanks to swanson)