Desmos - A beautiful, innovative, and modern online graphing calculator.
SciDaVis - SciDAVis is a free application for Scientific Data Analysis and Visualization.
WolframAlpha - WolframAlpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels.
LabPlot - LabPlot is a KDE-application for interactive graphing and analysis of scientific data.
GeoGebra - GeoGebra is free and multi-platform dynamic mathematics software for learning and teaching.
DataMelt - DataMelt (DMelt), a free mathematics and data-analysis software for scientists, engineers and students.