Dev{School} codelabs provide guided, tutorial, hands-on coding experiences. Most codelabs will step you through the process of building a small application, or adding a new feature to an existing application. They cover a wide range of topics such as HTML, CSS, JavaScript, AngularJs and Polymer
You should be able to complete any of them in your favorite development environment. Just pick a codelab about a topic that you find interesting and follow the instructions.