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.

GLE is a library package of C functions that draw extruded surfaces, including surfaces of revolution, sweeps, tubes, polycones, polycylinders and helicoids. Generically, the extruded surface is specified with a 2D polyline that is extruded along a 3D path. A local coordinate system allows for additional flexibility in the primitives drawn. Extrusions may be texture mapped in a variety of ways. The GLE library generates 3D triangle coordinates, lighting normal vectors and texture coordinates as output. GLE uses the GL or OpenGL API's to perform the actual rendering.

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.

graphviz is a set of graph drawing tools and libraries. It supports hierarchical and mass-spring drawings; although the tools are scalable, their emphasis is on making very good drawings of reasonably-sized graphs. Package components include batch layout filters and interactive editors for X11, Java, and a TCL/tk extension. The batch filters can be configured as a web visualization service (using GIF and click-maps). Typical applications include display of finite state machines, software diagrams, database schemas, and communication networks.

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.

The GNU Triangulated Surface Library (GTS) provides a set of useful functions to deal with 3D surfaces meshed with interconnected triangles. It features metric operations (area, volume, curvature, etc.), 2D Delaunay and constrained Delaunay triangulations, robust geometric predicates and set operations on surfaces (union, intersection, etc.), surface refinement and coarsening (multiresolution models), and bounding-boxes trees for collision/intersection detection.

A portable cross-platform library and a set of applications for chiptunes playback.