LabPlot is a free software data analysis and visualization application built on the KDE Platform. It integrates well into a KDE workspace but can just as well be used in another desktop environment.
You can use LabPlot to produce publication quality plots of your data in addition to modeling mathematical functions. The latest stable release is LabPlot 1.6, based on KDE 3. However a port to KDE Platform 4 is in progress.
LabPlot allows you to import Origin data files and export plots to many different formats. LabPlot is distributed under the terms of the GNU General Public License.