Does anybody know of some programs I can use to make diagrams that look like the following
I would use the above diagram directly, however due to copyright issues, this is not an option for me. What is the most painless way I can do this and make similar diagrams as well? If standard MS Office tools can, please share that information as well.
I'd suggest PgfPlots for the best results in terms of quality and harmony with the rest of your documents. Another nice tool is Python's MatPlotLib (which supports Bezier curves drawing), which supports LaTeX style in titles, formulas, axis labels ecc...You could also use Inkscape, which can produce directly Tikzpicture environments if you use the code you find here
I would import the drawing into Inkscape, an trace it. This shoul lead to an acceptable result. Although, reading the data from the chart and replotting using Excel could be less work, as was already suggested in the comments.