Every October, DigitalOcean organizes Hacktoberfest, a program encouraging you to contribute to open-source projects (and rewarding you with stickers & a super cool shirt). Multiple organizations will also give you swag if you contribute to their repositories on Hacktoberfest. Like last year, here's a list of all the organizations I've been able to find this year:

• Official Hacktoberfest - Register on the website, make 5 PRs to any repository, get swag. Reference
• Orbtoberfest by CircleCI - Make pull requests to CircleCI repositories and fill this form to get stickers & a limited edition shirt. Reference
• Appwrite - Get a pull request merged into any Appwrite repository and you'll get stickers, magnets & buttons. Reference
• Uno - Get a PR merged to any Uno Platform repository and fill in this form. Reference
• Accord - Make two PRs to Accord repos to get stickers, more to get a shirt. Reference
• Operation Code - Make a PR and get stickers, close three issues and get a shirt. Reference
• Hasura - Make a Pull Request to any Hasura repository to get some stickers and two PRs to Hacktoberfest repositories to get a shirt. Reference
• Parity - Fill in this form, then solve four Hacktoberfest-tagged issues or tackle a big one. Reference
• Umbraco - Get one PR merged to any Umbraco repository to get some swag. Reference
• Valor Software - Make a pull request to ngx-bootstrap to get a pen and a sticker, and three to get a notebook. Reference
• Twilio - Get a PR merged to any twilio-labs repository to get some stickers and two or more to get Twilio socks. Reference
• MayaData - Get swag for contributing in general. At the end of the month, the individual who makes the most significant contributions will get a brand-new laptop. Reference
• JabRef - Get stickers for getting one PR merged to JabRef repositories, and a shirt if you get five. Reference
• LBRY - Get a sticker for any kind of contribution to LBRY repos, and a shirt for meaningful contributions. Reference
• Squashtoberfest by Adobe & Magento - Submit 5 or more PRs to any Adobe or Magento repositories to get a shirt and some swag. Reference

I strongly encourage you to participate. You don't even need to know how to code, in most cases fixing a typo in the documentation or adding examples to the README will be enough to get you some nice stickers.

Have fun, and happy Hacktoberfest!