LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
Matchering - Open-source audio mastering app that masters music based on any reference track you provide.
QCAD - QCAD is an application for computer aided drafting in 2D.
eMastered - eMastered makes a song sound better through online mastering.
FreeCAD - An open-source parametric 3D modeler
Audio Mastering - Pro quality, fully functional audio mastering application for iPad.