LibreOffice Calc is the spreadsheet program you've always needed. A fork of OpenOffice.
Graphviz is open source graph visualization software. It has several main graph layout programs.
Data analysis and graphing software for scientists and engineers. It provides You with dozens of functionalities and options.
Prism is an analysis and graphing solution purpose-built for scientific research.
InfraNodus can visualize any research notes, ideas, texts, even the Google search results on a certain topic as a text network.
AxGlyph - Scientific and Educational Graph Editor.
SigmaPlot is a proprietary software package for scientific graphing and data analysis for Microsoft Windows.
The software can read multiple formats and perform mathematical transforms and statistical analyses.