Audio converter and CD ripper for various formats
fre:ac is a free audio converter and CD ripper for various formats and encoders. It features MP3, MP4/M4A, WMA, Ogg Vorbis, FLAC, AAC, and Bonk format support, integrates freedb/CDDB, CDText and ID3v2 tagging and is available in several languages.
a parametric 3D CAD modeler
WARNING: FreeCAD has moved! FreeCAD code and release files are now hosted on github at https://github.com/FreeCAD/FreeCAD Only older files and code are available here. FreeCAD is a general purpose feature-based, parametric 3D modeler for CAD, MCAD, CAx, CAE and PLM, aimed directly at mechanical engineering and product design but also fits a wider range of uses in engineering, such as architecture or other engineering specialties. It is 100% Open Source and extremely modular, allowing for very advanced extension and customization. FreeCAD is based on OpenCasCade, a powerful geometry kernel, features an Open Inventor-compliant 3D scene representation model provided by the Coin 3D library, and a broad Python API. The interface is built with Qt. FreeCAD runs exactly the same way on Windows, Mac OSX and Linux platforms.
A circuit simulator with graphical user interface (GUI)
Qucs is a circuit simulator with graphical user interface. The software aims to support all kinds of circuit simulation types, e.g. DC, AC, S-parameter, Transient, Noise and Harmonic Balance analysis. Pure digital simulations are also supported.