You can have Tooltips on mouse-over showing the data point value or something else.
To add a Tooltip, you need to use an expression in the Pivot >> Data Groupings >> Values >> Action tab, Tooltip field
For example, if the Value for your bar series (in the Pivot >> Data Groupings >> Values >> General >> Data) has an expression like: =SUM(Fields!Value), you need to use the same expression in the Action tab >> Tooltip
You can have more complex expressions for showing Tooltips. For example, the following topic explains how you can use parameters interactive drill-down chart and also have Tooltips based on these parameters: http://support.nevron.com/KB/a203/create-interactive-drill-down-chart-in-sharepoint.aspx
Nevron Support Team