Nothing feels less productive than fighting with Git. The official documentation is the real problem: it's roughly as arcane as Norse runes.* I managed to find a few tutorials today, at least:

• Atlassian Git tutorial - just a basic rundown of the common commands.
• Try Git - I find that the Github documentation is just as bad as the Git docs: it makes the basics sound easy but doesn't provide enough detail to know what to do when things go totally wrong. This does the same thing in an interactive way. It's great for the basics but not much more than that.

*They all read like this.