Jmol is a Free, Open Source molecule viewer and editor. It is a collaboratively developed visualization and measurement tool for chemical scientists. Jmol is an active project, and there are new features being added to it on a daily basis. Users are encouraged to modify it to fit their needs and to contribute their changes to the project.
FrAid (Fr[actal] Aid) is a programming language that is appropriate for mathematical computations, visualization, batch processing, and more. It features both a standalone application that provides a programming environment for the language and a system for integrating the language with Java. The Java interface allows mathematical equations and formulas to be used with Java code, making it easier to process numerical computations, symbolic computations, imaging, CAD, and more.
X-Plane is a flight simulator that reads in the geometric shape of any aircraft and then figures out how that aircraft will fly. It does this via an engineering process called "blade element theory", which involves breaking the aircraft down into many small elements and then finding the forces on each little element many times per second. These forces are then converted into accelerations, which are then integrated to velocities and positions. This gives X-Plane the most realistic flight model available for personal computers.
linSmith is a Smith charting program. Users can enter either discrete components or transmission lines, see the results on screen, and/or generate Postscript output. Component values can be changed numerically or using scrollbars. Problems can be solved on-screen, and high-quality Postscript can be output for publication.
OpticalRayTracer analyzes systems of lenses. It uses optical principles and a virtual optical bench to predict the behavior of many kinds of ordinary and exotic lens types. It includes an easy-to-use interface that allows the user to rearrange the optical configuration by simply dragging lenses around using the mouse. It fully analyzes lens optical properties, including refraction and dispersion. The dispersion display uses color-coded light beams to simplify interpretation of the results.
Mathnetics is an API for creating advanced, interactive, Web-based mathematical applications. It defines various important mathematical objects that are inter-related and on which many numerical calculations can be done. It also features rendering of 3D objects onto an SVG canvas (to do so, it includes certain utilities such as browser sniffing, DOM node selection, and DOM readiness detection), which is quite robust. A few basic 3D objects are given (Line, Sphere, Cube), but the user can define any 3D object desired as per the specification.