CSS Frameworks for Responsive Web Design

Responsive Web design (RWD) has taken the 'Net by storm. RWD isn't just trendy among designers, it's useful to ensure a consistent user experience - something of increasing important with the diversity of screen sizes today. Fortunately, there are some incredibly useful resources available (like CSS Frameworks) for designers and developers to create digital products in some terrifically exciting ways.

CSS Frameworks are essentially pre-prepared libraries which simplify standards-compliant styling of web pages using the CSS (Cascading Style Sheets) language. Much like libraries for other programming and scripting languages, CS frameworks are incorporated as external .css sheets referenced in the HTML. So what are the very best CSS frameworks available to design and developers today?

Foundation 3 - Built with Sass, a CSS preprocessor, the CSS Framework offers a flexible, nestable system, multi-device compatability and more.

Responsive.GS - Offers 12,16, and 24 column layout grids with media queries for all standard devices.

960 Grid System - Based on a width of 960 pixels, offers 12 and 16 column grids, includes templates for Photoshop and GIMP, InDesign; ideal for rapid prototyping.

Gumby Framework - A pliable (fluid and fixed) framework providing support for new HTML5 elements, includes PSD layouts and an optional UI kit. 

Blueprint CSS Framework - Offers an easily customizable grid, "sensible" default typography, scripts for customization.

There are of course many others CSS frameworks which are most definitely worthy of additional exploration, including: 

IngridYUI 3 CSS GridResponsive Grid SystemTitan Framework