OpenDX is a uniquely powerful, full-featured software package for the visualization of scientific, engineering and analytical data: Its open system design is built on a standard interface environments. And its sophisticated data model provides users with great flexibility in creating visualizations.
PGF is a TeX macro package for generating graphics. It is platform- and format-independent and works together with the most important TeX backend drivers, including pdftex and dvips. It comes with a user-friedly syntax layer called TikZ.
Agna is a freeware application designed for social network analysis, sociometry and sequential analysis. Platform-independent, friendly and easy-to-learn, integrated visual network editor, html output, free.
Vis5d+ is intended as a central repository for enhanced versions and development work on Vis5d, a free OpenGL-based volumetric visualization program for scientific datasets in 3+ dimensions. This project started out, with the blessing of the original Vis5d developers, as a conversion of Vis5d's build process to use GNU autoconf and automake. (Inspired by the difficulty of getting Vis5d to compile on the author's LinuxPPC PowerBook.) It quickly became apparent that many other enhancements were possible, and were of wide interest to users. Moreover, a large number of enhanced versions to Vis5d exist that have not been merged into the original Vis5d sources, due to time and resource limitations of the original developers, or to differences of opinion about design directions
Graph Visualization
Graph visualization is a way of representing structural information as diagrams of abstract graphs and networks. Automatic graph drawing has many important applications in software engineering, database and web design, networking, and in visual interfaces for many other domains.
Graphviz is open source graph visualization software. It has several main graph layout programs. See the gallery for some sample layouts. It also has web and interactive graphical interfaces, and auxiliary tools, libraries, and language bindings.