Some links:
https://github.com/MunGell/awesome-for-beginners
https://gauger.io/
https://24pullrequests.com/
http://issuehub.io/
http://www.pullrequestroulette.com/
https://goodfirstissues.com/
https://www.firsttimersonly.com/
https://up-for-grabs.net/#/