“Git Immersion is a guided tour that walks through the fundamentals of Git, inspired by the premise that to know a thing is to do it.”
tutorials
Khan Academy
"The Khan Academy is a not-for-profit 501(c)(3) with the mission of providing a world-class education to anyone, anywhere. Despite being the work of one man, Salman Khan, this 1600+ video library is the most-used educational video resource as measured by YouTube video views per day and unique users per month. We are complementing this ever-growing library with user-paced exercises–developed as an open source project–allowing the Khan Academy to become the free classroom for the World."