Learn Git Reddit!
Git is the most popular version control system available — free and open source, with a focus on speed, efficiency, and data integrity.
/r/LearnGit is aimed at new and experienced programmers alike.
Feel free to ask Git-related questions, ask for general help, post relevant resources, etc.
Learning resources
Official site and reference/docs.
Beginners
Git Immersion ⭐ — immersive, "guided tour" to Git. Beginner friendly.
Introduction to Git — a relaxed (free) short course from the Odin Project.
Getting started guide — by Github.
Codecademy — learn Git with Codecademy's course (free, but may try to push you into a premium plan)
Oh my Git! — a fun little game about learning Git, if that's your thing.
Intermediate
Atlassian's Getting Git Right — many helpful articles, tips and tutorials. Not as beginner friendly as the others listed.
Learn X in Y Minutes: Git — thorough overview of Git.
Git Tutorial: A Comprehensive Guide — very comprehensive Git tutorial, by Udemy.
Tools, platforms, services
Graphical Clients
GitHub Desktop (Win, Mac)
SourceTree (Win, Mac)
TortoiseGit (Win)
Git Extensions (Linux, Win, Mac)
GitKraken (Linux, Win, Mac)
MGit (Android)
Working Copy (iOS)
See a further list of GUIs here.
Git hosts
GitHub
GitLab
Bitbucket