Andrey Savchenko, known as Rarst in the WordPress community, has built a great guide to using Composer in WordPress. Composer is a dependency management tool for PHP projects. It brings a ton of power to the table, and this resource is great for any of us getting started with using Composer in our WordPress projects.
I have a lot to learn, and plan to use this to do it. When I wrote recently about the need for code dependency in WordPress, I didn't even understand what Composer was. Well, as I quickly learned, it turns out Composer was the answer to the needs I described.