Engauge Digitizer - This open source, digitizing software converts an image file showing a graph or map, into numbers.
DigitizeIt - Sometimes it is necessary to extract data values from graphs, e.g.
DataThief III - DataThief III is a program to extract (reverse engineer) data points from a graph.
GraphClick - GraphClick is a graph digitizer shareware for Mac OS X which allows to automatically retrieve the original (x,y)-data from the image of a scanned graphor fom QuickTime movies.
im2graph - im2graph graph digitizing software to convert graphs to numbers
Silkscientific UN-SCAN-IT - Digitizing Software converts graph image files to usable (x,y) data automatically