DigXY

From Thunderhead Engineering Consultants:

DigXY is a digitizer with a simple interface that allows you to extract data of a graph or chart. You can open the graph image in several popular formats, or use built-in scanner support to scan the plot directly into DigXY for digitization. It's easy to digitize values, even if the image is rotated. Also supports linear or logarithmic axes and works well with contour plots, scatter plots, and photos. Collected data points are shown in a spreadsheet view and can be pasted directly into Microsoft Excel or any other spreadsheet or text editor.