gnuplot is a popular scientific plotting package.
After an enormous time of more than 5 years, the gnuplot development team is proud to present to the world the first major version update of gnuplot since before the internet (well, almost ;-). See the release notes in the File release system for details. Places to learn about the new release include:
http://www.gnuplot.info/
htpp://gnuplot.sourceforge.net/
http://sourceforge.net/projects/gnuplot/