Google Gadgets - predated the visualization toolkit... (http://code.google.com/apis/visualization/documentation/gallery.html)
 

Here's a nice flash tool helpful for zooming in and out of a time series analysis:

 

 

This is an example of water level readings collected over many years with variable data resolution.  The increased recent frequency in recent years reflects interest in local trends.  Being able to visualize the entire dataset is important because the recent increased frequency of sampling doesn't capture the larger trend.