You might also like:
gnuplot http://www.gnuplot.info/
matplotlib http://matplotlib.org/
Origin http://www.originlab.com/
Timing Diagrammer Pro http://www.syncad.com/timing_diagrammer_timing_diagram_editor.htm
IgorPro http://www.wavemetrics.com/
Logic analysers:
piscope http://abyz.co.uk/rpi/pigpio/piscope.html
Saleae Logic https://www.saleae.com