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.

Check out the contributing documentation and find prepared issues on hoodie.camp.

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.

Read more about the inspiring history of HospitalRun and about how to contribute.

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.

Botkit is a framework for designing and developing useful, creative bots for messaging platforms like Slack, Facebook Messenger, and the Microsoft Bot Framework.

If you've got skills in JavaScript and Node.js, check out the open issues and the contributing guide.

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).

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.

Atom is a modern, hackable text editor built with web technologies like JavaScript, HTML and CSS. It ships with a menagerie of packages and themes, along with a package manager to let you handle it all seamlessly.

If you want to get involved, check out Making Your First Contribution on the Atom blog.

Batavia is part of the larger BeeWare project, which aims to make it easy for Python developers of all skill levels to develop rich, native user interfaces. Batavia is the software that lets you run Python bytecode in your browser. So it's Python, but it's also JavaScript.

Batavia has documentation for first time contributors, as well as a contributing guide aimed at more seasoned hands.

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.

To start contributing, find a sprint happening near you, or check out the contributing documentation and find the community online.

Node.js is a runtime built on Chrome's V8 JavaScript engine, bringing the most common frontend language to the backend.

There are many ways to get involved by contributing to both the code itself, the ecosystem, or the broader Node.js community.

The Node.js community runs a series of live events to help people get started contributing.

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.

The best places to get started are the contributing guide and issues labeled "help wanted"

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.

Zulip is a powerful, open source group chat application that combines the immediacy of real-time chat with the productivity benefits of threaded conversations. Zulip is used by open source projects, Fortune 500 companies, large standards bodies, and others who need a real-time chat system that allows users to easily process hundreds or thousands of messages a day. With over 700 contributors merging over 500 commits a month, Zulip is also the largest and fastest growing open source group chat project.

Check out our guide for new contributors to get started. Zulip prides itself on maintaining a clean and well-tested codebase, and a stock of hundreds of beginner-friendly issues.

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 Start Here Repo. And if you have other skills, they could also use help with mentoring, fundraising, PR/branding, and grant writing. You will find beginner friendly Issues labeled in their repos.