My colleague, NM, recommended this course $$$:
Git & GitHub – The Practical Guide
Learn Git & GitHub and master working with commits, branches, the stash, cherry picking, rebasing, pull requests & more!
Git and GitHub Tutorial for Beginners [11 Hours], YouTube (11:12:59) by Bogdan Stashchuk (who additionally has a $$$ course)
Git Immersion (“a guided tour that walks through the fundamentals…”)
Git Anatomy by Dino Esposito at Redgate
Git Internals by Scott Chacon at PeeCode Press {now PluralSight} (121pp)
Pro Git by Scott Chacon and Ben Straub by Apress (free ebook)
Version Control with Git by dbt (I really like this workflow diagram they created) 
Git, GitHub, & Workflow Fundamentals by Molly Nemerever (I like the diagram she posted, too)
And she refers to this site, Getting Started with Git by Josh Errickson also
Welcome to Learn Git Branching
Git Workflows for Pros: A Good Git Guide by Joe James (contains several team workflow diagrams to consider)
Git cheatsheet from PhoenixNAP 
Git cheatsheet from Intellipaat 