Bootstrap
If you want to give your new project a professional look and feel, Bootstrap might be the tool you need. If features a very clean typography, form elements as well as almost all you need to design a modern website.
More info: http://twitter.github.io/bootstrap/index.html
Foundation
Brought to you by Zurb, Foundation is a very interesting tool which is perfect for creating responsive webpages. Foundation comes with a lot of different layout templates so you’ll definitely save many time when starting your new project.
More info: http://foundation.zurb.com/
Compass
Compass is an open-source CSS authoring framework. It uses Sass, an extension of CSS3 which adds nested rules, variables, mixins, selector inheritance, and more. Definitely worth giving a try!
More info: http://compass-style.org/
Profound Grid
Here is a responsive grid system for fixed and fluid layouts, all built in SCSS. If you’re planning to develop a layout based on a grid, you should definitely have a look at Profound Grid.
More info: http://www.profoundgrid.com/
Kube
Kube is a simple and minimalistic CSS framework based on a flexible grid and beautiful typography. Probably the right tool for you if you’re looking for a lightweight framework with no imposed styling!
More info: http://imperavi.com/kube/
Topcoat
I know that I already wrote about Topcoat a lot on CWC lately, but really, Topcoat is awesome! A great CSS framework if you want to be able to create a professional looking website quickly and easily.
More info: http://topcoat.io/
Skeleton
Skeleton is a small collection of CSS files that can help you rapidly develop sites that look beautiful at any size, be it a 17″ laptop screen or an iPhone.
More info: http://www.getskeleton.com/
Pure CSS
Pure is a set of small modules that you can use as a basis for almost every web project. It features grids, forms elements, menus, tables and a lot more.
More info: http://purecss.io/
KNACSS
KNACSS is a minimalist, responsive and extensible CSS framework to kick-start your HTML/CSS projects.
It handles basic elements, box sizing, margins, floats, simple and complex aligns, positioning, layout grids, gutters, old IE fallbacks and last but not least responsiveness, everything automagically!
More info: http://www.knacss.com/
Metro UI
Do you like the Windows 8 style? If yes I bet you’ll enjoy Metro UI, a CSS framework which allow you to create websites with a Windows 8 look and feel.
More info: http://metroui.org.ua/