Git is the most important tool for professionals. It or some other type of Source Code Control.
Can use github for public projects and bitbucket offers private/public repos for single users/small groups.
GitHub - Free public repos
BitBucket - Free private/public repos up to 5 users.
15 online interactive Try Git - Provides a sandbox to try Git out and practice.
git-the simple guide - This one is probably best to start out.
Git-book free - Covers git in depth.
Gentle Intro to GIT - sounds like it's a starter guide but it covers some advanced concepts.
Branching Model -- more advanced, covers the concept of branching with examples.
Workflows
Each of the providers above also have help specific to their services.
On windows, there's programs for git. GIT Bash /GUI is what I use.
You don't have to have an account @ github or bitbucket to start but you will want one for your own projects.
Source Code Control lets you maintain different versions of your code. You commit code and can revert to previous versions. It helps to manage code bases with multiple contributors. It should be part of any professional development process.
If you want a practical reason to use git, GitHub Pages provides static hosting and uses github to store the html/css/js. It's free. Lots of people use it for online resumes or in some cases, projects use it to host their release websites.