Detour - Immersive audio walks, now in 17 cities
SketchUp - 3D for Everyone
Airbnb Trips - Travel and experience trips with locals
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
Party with a Local - Party with a Local is a free app that connects travelers with locals that want to party.
FreeCAD - An open-source parametric 3D modeler