Ask HN: What is the “hello world” or “to do list” of Bitcoin

I want to learn the basics of bitcoin. I am pretty limited in my skillset as a developer, but am really interested in this technology and am looking for a small project to get started on. I can code javascript and ruby, and know basic js frameworks(angular, jquery, handlebars, rails, etc.) I just want to learn so would be willing to take on learning more, and would be excited. Basic app ideas and resources would be super helpful.