Wikipedia
Ploticus
Ploticus is a free, open source ( GPL) computer program for producing plots and charts from data. It runs under Unix, Solaris, Mac OS X, Linux, and Win32 systems. Community support is customarily done through Yahoo News Groups. Bruce Byfield in Linux.COM described Ploticus as, "...a throwback to the days when Unix programs did one thing, and did it well, using a minimum of system resources."