LabPlot - LabPlot is a KDE-application for interactive graphing and analysis of scientific data.
GnuPlot - Gnuplot is a portable command-line driven interactive data and function plotting utility.
SciDaVis - SciDAVis is a free application for Scientific Data Analysis and Visualization.
Giac/Xcas - Free computer algebra system
DataMelt - DataMelt (DMelt), a free mathematics and data-analysis software for scientists, engineers and students.
Geometry Pad - Geometry Pad is a dynamic geometry application for iPad and Android tablets.