Sites like psi-im.org

Gajim, a free desktop chat app for the XMPP messaging protocol, with synchronized chats across devices

Converse, an open-source web-based XMPP chat client and embeddable messaging library with documentation for developers

Cheogram is a messaging service that connects telephone SMS and open chat networks such as XMPP and Matrix into one app

IM Observatory, a discontinued 2013 security-testing tool by researcher Thijs Alkemade for the Jabber/XMPP instant messaging network

A Go software co-op's collection of XMPP libraries and tools, including the mellium.im/cli and mellium.im/xml packages

Stephen Paul Weber's personal website: blog essays on technology and inequality, software projects, standards work, and his resume

Movim, a decentralized social network and chat platform built on the XMPP protocol, for communication across devices

DietPi, a lightweight minimal Debian operating system image for single-board computers, with a blog, documentation and usage statistics

OMG! Ubuntu is a news blog covering Ubuntu and Linux apps, desktop software and open-source tips, written independently

Jonathan Snook's personal site, a blog, journal and web design and code playground at Snook.ca

The Battle for Wesnoth is an open source, turn-based fantasy strategy video game, with its project's developer documentation and release notes

An international community developing free and open-source software, including the Plasma desktop and KDE applications

A German news and commentary blog on privacy, digital rights, gaming and surveillance, with a satirical monthly review, Tarnkappe.info

BleachBit, an open-source disk cleaner and file shredder for Windows and Linux systems, with its help and documentation pages

The Activity Workshop is an English-language website of information on outdoor activities such as skydiving, paragliding and GPS, with translation tools and 3D hike plots

The official home of Xfce, a lightweight desktop environment for UNIX-like operating systems, with release news and blog posts

OpenRepos.net is a community repository of third-party applications for Linux mobile platforms such as Sailfish OS and Nemo Mobile

Personal website of translator and writer Thom Holwerda, managing editor of the technology news site OSNews.com since 2006

Conduit: a simple, fast chat server software project for hosting your own Matrix messaging server

GCompris is a free educational software suite for children, with activities for learning on computers

Manyverse, a free open-source peer-to-peer social network app for desktop and mobile, documented by its volunteer contributors, led by Andre Staltz

The Slackware Linux Project, a site documenting the Slackware Linux distribution with downloads, installation help, package lists, changelogs, FAQ and a book

Subclassed, a Mac and iOS app developer by Stefan Keller, making utilities that convert contacts and calendars

Bromite, a privacy-focused Chromium fork for Android with built-in ad blocking, run by a volunteer project

F-Droid is an app store and distribution platform for free and open source Android apps

Slax, a compact portable Linux operating system that runs from USB, with a blog by its author Tomas M

A personal blog on software, embedded systems and Rust, plus the author's own projects

Personal home page of Eric S. Raymond hosting his open-source software, FAQs, essays and the Retrocomputing Museum

A BitTorrent client called Deluge, with GTK, web and console interfaces, for Linux, macOS, Unix and Windows

Manjaro, a Linux distribution built on Arch with rolling releases, with news and team pages by its core developers

The GNOME project's website, presenting its free and independent desktop computing platform and its community, in English and several other languages

Crystal Dew World is a site of software tools and dev support for CrystalDiskInfo and CrystalDiskMark, with news and Japanese-language pages by Crystal Dew

An open-source photo viewer app called ImageGlass for Windows, macOS and Linux, with a Pro edition, by developer Dương Diệu Pháp

BorgBackup, an open-source deduplicating backup archiver with compression and authenticated encryption, with documentation, release series and support pages

André Staltz's personal blog on software, open source, decentralization, programming and talks, with essays and conference talk listings

Nook Browser, an open-source privacy-focused web browser project, with release notes, roadmap and team pages by its developers

Grml.org: the project site for Grml, a Debian-based bootable live Linux system with system administration tools, plus its documentation and FAQ