CSS is not magic but shortcuts are great. Frameworks gather common patterns and make them available. Some are more libraries than frameworks.
Which to use and when
Bootstrap, Foundation and partly Pure are what we could call styled. That is to say, if you’re looking for a quick start they provide excellent design choices out of the box but if your design varies a lot you could end up spending all your time fighting the framework instead.
Bootstrap is the only one written with Less but there are Sass ports. SUIT and inuitcss share an approach that allows you to use everything or only parts of them as a basis for your own CSS. Also see this technical comparison of common patterns in frameworks
Here are some CSS frameworks that are actually worth using.
- SUIT - HTML/CSS framework for creating loosely coupled UI components
- inuitcss - a powerful, scalable, Sass-based, BEM, OOCSS framework.
- Pure - a well written low-level CSS framework by the people at Yahoo.
- Bootstrap - sleek, intuitive, and powerful mobile first front-end framework for faster and easier web development.
- Foundation - the most advanced responsive front-end framework in the world.