highcharts

Check out http://drupal.org/project/field_analytics for another way of analyzing on data for not only Drupal nodes, but any fieldable entity type.

As a class-based field reporting API, Field analytics makes it easy to add additional reports per field type.

There is a submodule for Highcharts included (tying with the new 7.x-2.x Highcharts API), which adds charts visualization to the default tabular reports. This submodule is a good example of how to extend Field analytics with additional reporting on field usage and data.