clockspeed uses a hardware tick counter to compensate for a persistently fast or slow system clock. Given a few time measurements from a reliable source, it computes and then eliminates the clock skew.

sntpclock checks another system's NTP clock, and prints the results in a format suitable for input to clockspeed. sntpclock is the simplest available NTP/SNTP client.

taiclock and taiclockd form an even simpler alternative to SNTP. They are suitable for precise time synchronization over a local area network, without the hassles and potential security problems of an NTP server.

HelenOS is a portable microkernel-based multiserver operating system designed and implemented from scratch. It decomposes key operating system functionality such as file systems, networking, device drivers and graphical user interface into a collection of fine-grained user space components that interact with each other via message passing. A failure or crash of one component does not directly harm others. HelenOS is therefore flexible, modular, extensible, fault tolerant and easy to understand.

See also https://www.wisdomandwonder.com/emacs/11659/blogging-with-emacs%f0%9f%90%83-from-org2blog%f0%9f%a6%84-to-wordpress
for a description of org2blog.

An open source Global Navigation Satellite Systems software-defined receiver.
Based on GNU radio.

Skyfield computes positions for the stars, planets, and satellites in orbit around the Earth. Its results should agree with the positions generated by the United States Naval Observatory and their Astronomical Almanac to within 0.0005 arcseconds (which equals half a “mas” or milliarcsecond).

   Written in pure Python and installs without any compilation.
   Supports Python 2.6–2.7 and Python 3.3–3.5.
   Has NumPy as its only binary dependency, the fundamental package for scientific computing with Python, whose vector operations make Skyfield efficient.

Collection of FFT and related algorithm implementation in various programming languages.

mpsh is an experimental command interpreter for Unix systems written by Dave Fischer at the Center for Computational Aesthetics and distributed under the 3-clause BSD license.

Recently "Lama Bleu" has been working on a custom firmware image for the PlutoSDR. Installing custom firmware allows you to load up a pre-configured Linux system which already has a bunch of useful software installed. He writes that his version is not designed to have a nice GUI, but rather focuses on scripting and data acquisition software.

source code and wiki for GNU clisp, more up-to-date than the one on
https://clisp.sourceforge.io/ (on 2018-12-11 that had Current version: 2.49 (2010-07-07), whereas the git repository contains changes done 4 weeks ago.

A critical review of John Ousterhout's “A Philosophy of Software Design”.
The blog has other interesting articles, for example
http://www.pathsensitive.com/2018/01/the-three-levels-of-software-why-code.html