BRL-CAD is a powerful constructive solid geometry solid modeling system that includes an interactive geometry editor, ray-tracing support for rendering and geometric analysis, path-tracing for realistic image synthesis, network distributed framebuffer support, and image and signal-processing tools.
Coin is an implementation of Open Inventor. Open Inventor is the de facto standard API for retained-mode 3D graphics programming. Open Inventor has a highly extensible design, and has been designed to allow for rapid development of highly interactive 3D graphics applications in the fields of CAD, engineering, scientific computing, simulation, VRML, and visualization.
Flounder is a program to quickly visualize 4D data (x,y,z,t). It can produce isosurfaces, solid renderings, as well as 2D slices. Several data sets can be viewed simultaneously. Temporal data at a spatial location can be examined with output in several formats including PNG and GIF animations.
Ghemical is a molecular modelling software package with some nice 3D visualization tools. It supports methods based on both molecular mechanics and quantum mechanics (using MOPAC7, and MPQC for QM). The geometry optimization (for MM and QM) and molecular dynamics (for MM) algorithms are included. Ghemical is written in C++, and hopefully offers a good framework for a generic freeware molecular modelling tool.
GNU TeXmacs is a free wysiwyw (what you see is what you want) editing platform with special features for scientists. The software aims to provide a unified and user friendly framework for editing structured documents with different types of content: text, mathematics, graphics, interactive content. TeXmacs can also be used as an interface to many external systems for computer algebra, numerical analysis, and statistics. New presentation styles can be written by the user and new features can be added to the editor using Scheme.
Gri is an extensible plotting program designed for scientists. It can draw x-y plots, contour plots, and image plots, and has rudimentary programming capabilities. Output is PostScript. Gri is not mouse driven, nor GUI-based; it is a language. Users regard it as an analogue to the LaTeX document formatting language: users gain considerable power, at the price of a moderate learning curve.
GtkDatabox is a widget for the GTK+ library designed to display large amounts of numerical data quickly and easily. It allows for one or more data sets of thousands of data points (X and Y coordinates) to be displayed and updated in split seconds. It offers the ability to zoom into and out of the data, and to navigate through your data by scrolling. In addition to rulers and a simple coordinate cross, it allows you to add one (or even more) configurable grids like on an oscilloscope. Data may be presented as dots, lines connecting the data, or vertical bars. The widget allows you to easily transform pixel coordinates into data coordinates, thus allowing you to easily create powerful applications for data analysis.
GtkMathView is a GTK widget for rendering MathML documents. It is meant to be a standalone, light-weight component and not a full browser. GTK applications can use the widget as a window for displaying mathematical formulas and doing simple interactions. Among other features, GtkMathView includes support for breaking long mathematical expressions, rendering of stretchy operators, and provides a customizable support for additional fonts.