https://www.w3.org/Talks/Tools/Slidy2/ and https://www.w3.org/Tools/Ical2html/,  https://www.w3.org/People/Bos/Hcalproxy/ look interesting.

Alternative firmware for ESP8266 with easy configuration using webUI, OTA updates, automation using timers or rules, expandability and entirely local control over MQTT, HTTP, Serial or KNX. Full documentation at https://tasmota.github.io/docs
See also https://ota.tasmota.com/tasmota/release/

We currently support the processing of:

the United States' Global Positioning System (GPS);
the Russian GLONASS system (GLONASS);
the European Union's Galileo system (Galileo);
the Chinese Navigation Satellite System (BeiDou);
the Japanese QZSS develop system (QZSS).
We are actively developing Ginan to have the following capabilities and features:

Precise Orbit & Clock determination of GNSS satellites (GNSS POD);
Precise Point Positioning (PPP) of GNSS stations in network and individual mode;
Real-Time corrections for PPP users;
Analyse full, single and multi-frequency, multi-GNSS data;
Delivering atmospheric products such as ionosphere and troposphere models;
Servicing a wide range of users and receiver types;
Delivering outputs usable and accessible by non-experts;
Providing both a real-time and off-line processing capability;
Delivering both position and integrity information;
Routinely produce IGS final, rapid, ultra-rapid and real-time (RT) products;
Model Ocean Tide Loading (OTL) displacements.
The software consists of two main components: Network Parameter Estimation Algorithm (PEA) and Precise Orbit Determination (POD).

This project allows you to use various hardware security devices to operate GPG and SSH. Instead of keeping your key on your computer and decrypting it with a passphrase when you want to use it, the key is generated and stored on the device and never reaches your computer. Read more about the design on https://github.com/romanz/trezor-agent/blob/master/doc/DESIGN.md

Currently TREZOR One, TREZOR Model T, Keepkey, Ledger Nano S, and OnlyKey are supported.

Scalable from 8-bit to 32-bit microcontroller environments, the primary governing standards in NuttX are Posix and ANSI standards. Additional standard APIs from Unix and other common RTOS’s (such as VxWorks) are adopted for functionality not available under these standards, or for functionality that is not appropriate for deeply-embedded environments (such as fork()).

Zephyr is a new generation, scalable, optimized, secure RTOS for multiple hardware architectures.
A number of boards are supported, including the Raspberry π Pico https://docs.zephyrproject.org/latest/boards/arm/rpi_pico/doc/index.html

Software that aims to provide an easy to use (hopefully) universal blackbox for solving polynomials and secular equations.

Among its features you can find:
- Arbitrary precision approximation.
- Guaranteed inclusion radii for the results.
- Exploiting of polynomial structures: it can take advantage of sparsity as well as coefficients in a particular domain (i.e. integers or rationals).

It can be specialized for specific classes of polynomials. As an example, see the roots of the Mandelbrot polynomial of degree 2.097.151 computed in about 10 days on a dual Xeon server.

If you use MPSolve in your research, please cite it as follows:
Bini, Dario A., Fiorentino, Giuseppe, Design, analysis, and implementation of a multiprecision polynomial rootfinder. Numerical Algorithms 23.2-3 (2000): 127-173.
Bini, Dario A., and Robol, Leonardo. Solving secular and polynomial equations: A multiprecision algorithm. Journal of Computational and Applied Mathematics 272 (2014): 276-292.
Found via https://en.m.wikipedia.org/wiki/Aberth_method and https://en.m.wikipedia.org/wiki/MPSolve
See also the GitHub repository http://github.com/robol/MPSolve.git A simpler implementation of the Ehrich-Aberth-method can be found in https://github.com/robol/ea-roots

Password manager based on Emacs' org-mode. Found on https://www.emacswiki.org/emacs/PasswordGenerator

You supply an antenna and a complex (I/Q) mixer to convert the radio spectrum to a low IF. Then send that IF to your computer using the sound card, Ethernet or USB. The Quisk software will read the I/Q data, tune it, filter it, demodulate it, and send the audio to headphones or speakers. Quisk has a microphone input and a key input so it can operate as a complete transceiver.

mpmath is a free (BSD licensed) Python library for real and complex floating-point arithmetic with arbitrary precision. It has been developed by Fredrik Johansson since 2007, with help from many contributors.