FreeCAD - An open-source parametric 3D modeler
NAPS2 - NAPS2 is a document scanning application with a focus on simplicity and ease of use.
SketchUp - 3D for Everyone
Simple Scan - Project information. Part of: The Gnome Project. Maintainer: Simple Scan Development Team. Driver: Simple Scan Development Team. Licence: GNU GPL v3.
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
XSane - A good proposal for SANE-2 has been written.