SciDaVis - SciDAVis is a free application for Scientific Data Analysis and Visualization.
LabPlot - LabPlot is a KDE-application for interactive graphing and analysis of scientific data.
OriginLab - OriginLab is a data analysis tool that provide the engineers and scientist with the technical charts and system for 2D and 3D plotting and all kind of fitting including curve and peak fitting.
IGOR Pro - Technical graphing and data analysis for Macintosh and Windows.
DataMelt - DataMelt (DMelt), a free mathematics and data-analysis software for scientists, engineers and students.
Kst - KDE Homepage, KDE.org