CSS - Libraries
All projects should have at least normalize.css. Basic standardization between browsers. Most other libraries have this included. Reset is not as nice as normalize as reset fills elements with multiple layers of styles, making inspecting more troublesome.
Bootstrap is the most common CSS library and for a reason. It provides basic standardized elements that you will need for your website. Just, don't edit the Boostrap's source code, please. If you need to change the appearance, include extra CSS/SASS files and encapsulate your changes inside your own class.
When using Bootstrap, it's a good idea to consider adding extra libraries on top of it for widgets you know you will need.
- Fuel UX: Standardized checkbox, combobox, datepicker, radio, select list and spinbox. Infinite scroll, loader, pillbox, placard, search input, tree view.
- X-editable: For complex in-place editing popups.
- Yamm For complex megamenus like Amazon is using
- Jasny Side navigation menu, fixed alerts, off canvas menu, simple input mask, standardized file input widget.
- Bootswatch Themes for Bootstrap.
Font Awesome is the second most popular, introducing font icon to your project. You will probably need this for all web apps.
Animate.css provides basic CSS animations in a neat package.