FreeCAD - An open-source parametric 3D modeler
Procore - Procore is the world's most widely used construction project management software. Easy to use, mobile platform with unlimited user licenses.
SketchUp - 3D for Everyone
Corecon - Corecon offers integrated estimating, project management, and job costing for small to medium-sized construction companies.
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
PlanGrid - The #1 construction app. Used by thousands of companies to save time, money, and ditch paper plans forever.