IGOR Pro!

Gnuplot is a portable command-line driven interactive data and function plotting utility. It was originally intended as to allow scientists and students to visualize mathematical functions and data. It does this job pretty well, but has grown to support many non-interactive uses, including web scripting and integration as a plotting engine for third-party applications like Octave. Gnuplot supports many types of plots in either 2D and 3D. It can draw using lines, points, boxes, contours, vector fields, surfaces, and various associated text. It also supports various specialized plot types. »

QtiPlot is a professional scientific data analysis and visualisation solution. It is meant to be a cheap alternative to proprietary and costly software such as Origin, SigmaPlot, Regressi or Igor Pro.

SciDAVis is a free application for Scientific Data Analysis and Visualization. It's an application aimed at data analysis andpublication-quality plotting. It combines a shallow learning curve andan intuitive, easy-to-use graphical user interface with powerfulfeatures such as scriptability and extensibility. Quite extensive manual can be found here: http://scidavis.sourceforge.net/help/manual/index.html

Kst is a fast, real-time large-dataset viewing and plotting tool available and has built-in data analysis functionality.Kst is moreover expandable with plugins and extensions.

SigmaPlot is a scientific data analysis and graphing software package with an intuitive interface for all your statistical analysis and graphing needs that takes you beyond simple spreadsheets and helps you to produce high-quality graphs without spending hours in front of a computer.

JFreeChart is a free 100% Java chart library that makes it easy for developers to display professional quality charts in their applications.

MagicPlot Viewer is a unique cross-platform application for viewing plots and thumbnails from multiple text/ASCII files.

KaleidaGraph, the daily workhorse for graphing and data analysis.

Aveloy Graph is an application for graph creation / data visualization - fast, easy to use and interactive.