RightHand.DataSet.Visualizer is an MDI application that lets you inspect DataSet structure and its data plus tons of other useful operations on DataSet.
http://blog.rthand.com/page/Righthand-Dataset-Debugger-Visualizer.aspx
http://blog.rthand.com/post/2011/01/08/Righthand-DataSet-Visualizer-goes-10.aspx