Great for new contributors
These projects have a history and reputation for being welcoming to new open source contributors. Have you had a great experience as a new contributor on an open source project? We'd love to hear about it!
Docker is a containerization platform. It is a way to enable developers and sysadmins to build, ship, and run distributed applications and microservices by standardizing
environments and eliminating inconsistencies and busywork.
The project has a huge online and offline community, and there are many opportunities to contribute to both the project itself (issue triage, code, documentation, tests) and the community (mentorship, support, speaking, writing).
If you want to get involved, check out Making Your First Contribution on the Atom blog.
The Node.js community runs a series of live events to help people get started contributing.
Django describes itself as the Web framework for perfectionists with deadlines. It's a high-level Web framework in Python with a focus on speed, scalability, and security. Django has a rich ecosystem with thousands of packages and projects.
Rust is a systems programming language that is famous for—and takes great pride in—being fast and safe.
As with all programming languages, Rust needs help with much more than writing parsers and compilers and a standard library. The community is an important part of growing the adoption of a language: mentoring, speaking at conferences and meetups, helping out with workshops, and writing documentation and tutorials. Check out their community page for more information about how you can get involved.
Homebrew installs open-source software and other applications on macOS. If you're a developer using a Mac, you may well have used this software.
Development happens in Ruby with a smattering of Bash and troubleshooting in any variety of programming languages that Homebrew's formulas rely on.
Middleman is a static site generator built in Ruby. The beauty of static sites is that they're blazingly fast and easy to deploy. The other beauty of static sites is that they always need frontend developers who can help make gorgeous templates for people to use. Middleman also has a rich extension ecosystem, which always needs contributors.
Take a look at their community page to start contributing.
Botkit is a framework for designing and developing useful, creative bots for messaging platforms like Slack, Facebook Messenger, and the Microsoft Bot Framework.
Exercism is a platform where experienced and aspiring programmers can quickly ramp up their fluency in the basics of a new programming language. The project supports over 30 languages, with support for new languages added on a regular basis.
The easiest place to begin contributing to Exercism is the curriculum, since each programming language has its own stand-alone repository, and each exercise is isolated from the others.
Read more about how to contribute to the Exercism programming language tracks.
Python is a programming language that is demonstrably simpler than most, and incredibly powerful. It is used extensively in scientific computing, finance, games, networking, internet development, and in assembling pipelines of other programs.
The language has a reputation for being great for new programmers, and the project itself has a reputation for being great for new contributors.
The repository linked to here is a mirror, as the project is not actively developed on GitHub (this is scheduled to change sometime in 2017). They've got a comprehensive guide to contributing to the language.
HospitalRun is a beautiful, easy-to-use hospital management system built for developing world hospitals. The system is a full hospital information system and handles both patient care and the business of running a hospital. Due to the challenges of connectivity in some of the places where these hospitals are located, an important goal of the application is making it work just as well offline as online.
Hoodie lets web developers build applications without worrying about a backend.
You can contribute in a number of ways both online and offline: documentation and triage, workshops and meetups, talks and blog posts, and writing code to help improve the Hoodie server itself. You can also build plugins to extend its features.
Operation Code is a non-profit on a mission to get active military, citizen-soldiers, veterans and their families coding and building software. Thanks to their efforts, a number of code schools and developer training programs are now covered by the GI Bill.
They run a fellowship program, a mentorship program, and a scholarship program.
To get started contributing to the project, take a look at the Contributing Guide. And if you have other skills, they could also use help with mentoring, fundraising, PR/branding, and grant writing.