An award-winning drawing program for children of all ages
A simple LaTeX {picture} drawing tool
very good CAD software
2D CAD for precise drawing
Vector drawing program for LaTeX using PSTricks
Simple and intuitive 2D vector drawing for electronics and not only.
Syntax Tree Drawing Software (Linguistics)
Madeline 2.0 Pedigree Drawing Engine (PDE)
Free drawing software for Windows, Mac OS X, and Linux
Simple and basic whiteboard drawing app in html5.
dedalo is a 2d cad drawing software written in python3.