this freeware below is great to pick data out of published data/graph. Along with Endnote and Mathematica (well, google too) one of the top productivity tool.
If I were to implement it in Mathematica I would use a combination of Manipulate and Epilog, certainly not as efficient as the plot digitizer.
[Basic clicking on a plot to get point coordinates is in Mathematica. See
http://blog.wolfram.com/2008/03/11/get-coordinates-new-in-602/ - Forum Moderator]