Sites like coin-or.org

Sam Who's personal blog of visual programming essays on topics like Big O, hashing and Bloom filters

A Python plotting library documentation site for Matplotlib, covering static, animated and interactive data visualizations

SciPy, an open source Python library of algorithms for scientific computing, covering optimization, integration, interpolation, statistics and differential equations

Thor Vector Graphics (ThorVG), an open-source lightweight vector graphics engine and project site with release notes by Hermet Park

Ogre3D, an open source C++ 3D graphics rendering engine with news, community forums, a legacy wiki and support

A cross-platform C library and command-line tools for communicating with iOS devices, developed as free open-source software

NumPy project website: the official home of the open source Python library for numerical computing and N-dimensional arrays

Skforecast documentation: a Python library for time series forecasting with scikit-learn regressors, from the skforecast project

Scikit-learn, an open-source Python library of machine learning tools for predictive data analysis, with documentation, FAQ and installation guides

Personal site of economist Mauricio Vargas Sepúlveda, a PhD student, with blog posts on trade and R tools

disk.frame is an R package for larger-than-RAM data manipulation on disk, documentation, changelog and articles by its author, now soft-deprecated

Personal academic website of Fredrik Johansson, researcher in computer algebra, covering his Arb arbitrary-precision library, publications and thesis

The MacPorts Project's official site offering a package manager for installing open-source software on macOS and other Unix-like systems

pqxx.org is a personal software project site by Jeroen Vermeulen hosting libpqxx, a C++ PostgreSQL client library, plus other open-source tools

The Open Source Geospatial Foundation website, a nonprofit hub supporting geospatial open source software projects, their community, events and governance

OpenCV, the open-source computer vision library, with its services, training, partner program and blog, run by the OpenCV organisation

The HDF Group, a non-profit company maintaining the HDF5 data format and library for scientific and engineering data management

The Tally Room is an Australian election analysis blog and podcast by Ben Raue, covering voting systems, polls and results

A programming language called Gleam, a type-safe functional language running on the Erlang runtime, with its documentation and community pages

Open source framework for managing Zsh shell configuration, with bundled plugins, themes and helper functions, maintained by a community

SciML is an open source software organization building Julia tools for scientific machine learning, physics-informed AI and differentiable programming

DWSIM, an open-source chemical process simulator software project with tutorials, wiki and downloads, developed by Daniel Wagner Oliveira de Medeiros

Calibre, a free open-source e-book management software for converting, organising and syncing e-books across devices

conda-forge: a community-run GitHub organization of conda recipes, packages and the Miniforge installer for software distribution

Homebrew, a package manager for installing software on macOS, Linux and WSL from the command line

SWI-Prolog is an open-source Prolog development environment and programming language distribution with documentation and downloads

Vale, an open-source command-line prose linter that checks documents against team style guides, by Vale Labs

Box2D is a 2D physics engine for games, with a blog by its creator Erin Catto on game physics and programming

Dyne.org, a digital community and free software foundry blog covering open-source tools, art, ecology and decentralized networks, by Dyne.org

SportsDataverse is an open-source project of R, Python and Node.js packages and a free sports play-by-play data warehouse

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

A web framework for building scalable web applications in Java and Scala, with documentation and source code on GitHub

John Coene's personal website, with a book on JavaScript for R, R package documentation, and talk slides on R and Shiny

Pocoo, a former team of open source developers behind Python projects Flask, Sphinx, Jinja, Werkzeug and Pygments

Osmocom, an umbrella project developing open source software and tools for mobile communications networks, run on a Redmine project site