What started a short list became quite a big description, more details inside the post.
Antonio Ramirez has shared a guide how to add FontAwesome via Composer in Yii2 project as Asset Bundle.
Semantic UI - a toolkit for web UI with semantic layout. Actually looks more semantic and clear (in terms of HTML code) than Bootstrap.
Hand-picked registry of Node.js frameworks. Makes you a suggestion for mature framework to start with a little easier (according to specific of your needs).
PuPHPet - simple GUI to set up virtual machines Vagrant + Puppet for Web development.
Mobile-Detect - a lightweight PHP class for detecting mobile devices. Works like $detect->isMobile() etc., very handy for choosing a frontend rendering strategy based on this info.