Question 29853
I'll assume you are a Windows user. You really should say though.

If you are comfortable with console style input then gnuplot is pretty good http://www.gnuplot.info/

Else, I've heard (but don't have any experience with) that GraphCalc http://www.graphcalc.com/ is pretty good.

GnuPlot is definitly free, I don't know about GraphCalc.