Found on Sacha Chua's blog https://sachachua.com/blog/2024/09/2024-09-23-emacs-news/ which links to the author's post https://www.reddit.com/r/emacs/comments/1fmk6d4/my_solution_to_handle_excalidraw_in_orgmode/

Found on https://www.reddit.com/r/emacs/comments/1c70qez/emacs_successors/
kons-9 is a new 3D computer graphics and animation software system being developed as an open source project under the MIT license.

quiver is a modern, graphical editor for commutative and pasting diagrams, capable of rendering high-quality diagrams for screen viewing, and exporting to LaTeX via tikz-cd. See also the github page https://github.com/varkor/quiver

A small collection of tools for the X Window System. Found on https://wiki.xxiivv.com/site/catclock.html

https://github.com/larsbrinkhoff/its-presentation -
https://github.com/larsbrinkhoff/oscilliscious Vector graphics audio oscilloscope library.
https://github.com/larsbrinkhoff/emacs-history

A pic preprocessor in awk for drawing circuit diagrams.

Examples of simple audio and video synthesis in C.
The blog has many other interesting articles such as
http://nullprogram.com/blog/2017/10/06/     A branchless UTF-8 decoder
http://nullprogram.com/blog/2017/09/21/     Finding the Best 64-bit Simulation PRNG
http://nullprogram.com/blog/2017/09/15/     Blowpipe: a Blowfish-encrypted, Authenticated Pipe
https://nullprogram.com/blog/2020/05/15/   w64devkit: a Portable C and C++ Development Kit for Windows
https://nullprogram.com/blog/2020/01/22/   A Makefile for Emacs Packages
https://nullprogram.com/blog/2019/08/09/   Keyringless GnuPG

A large quantity of published data is available only in the form of plots and it is often difficult to extract numerical data accurately out of these pictures. There are several softwares available to aid this process, but most are either paid, difficult to use or lack some essential features. Also, many of the existing programs work only on a few specific operating systems and require installation by the user. Most programs only support 2D X-Y plots and so it is not possible to work with polar diagrams, ternary diagrams, microscope images or maps. With these issues in mind, WebPlotDigitizer was developed to be an easy to use, free of charge and opensource program that can work with a variety of plot types and images. This program is developed using HTML5 which allows it to run within a web browser and requires no installation on to the user's hard drive.
Distributed under the GNU General Public License Version 3.

Found on John D. Cook's blog
http://www.johndcook.com/blog/2016/04/20/how-to-digitize-a-graph/

Changed URL from http://arohatgi.info/WebPlotDigitizer/ 2019-12-30

Written in 91 lines of C, license is unclear.

Highcharts is a charting library written in pure JavaScript, offering an easy way of adding interactive charts to your web site or web application.
Free for non-commercial use. Found via
http://blog.tafkas.net/2012/10/03/gathering-and-charting-temperatures-using-rrdtool-and-highcharts/