If you need a base when starting a new project and don't want it to be complicated, Kube Framework can be a good choice.

The framework is a single CSS file that brings responsive layouts with no headache and offers more.

Kube includes styles for forms, grids, buttons, tables, typography and few other stuff like links or images.

For developers looking for maximum flexibility and customization, LESS files are also provided.

If you are one of the designers/developers who jumped into the LESS world to get more out of CSS, you will love Css2Less.

It is a web-based tool for converting CSS files into LESS by simply copy-pasting the styles.

The tool uses the css2less Ruby library in the backend and its website is open sourced for anyone willing to host it themselves.

Fiddle Salad is a fresh web development tool, an online IDE, for client-side web applications.

It allows us to write HTML, CSS, JavaScript code or use alternatives like HAML,Zen Coding, SASS, LESS and more.

All the code is written in a single-page interface and the output is displayed/rendered instantly.

There is built-in code completion support for CSS + jQuery and links to the documentation for the properties of each language.

With a free membership, it is possible to create any number of projects and save them for re-working on them without losing any settings or data.

If you already use it, then you know that LESS is a "time and byte-saver" when creating + serving stylesheets (if not, you should definitely check it).

You either use the .less files directly (via less.js or on the server with Node.js) or compile them into CSS from command-line and use only the CSS.

Crunch is a free Adobe AIR application that eases the compiling part without the need of command-line but via a user-friendly interface.

It is a simple CSS/LESS editor with syntax highlighting and multi-tab support.

Once a LESS file is saved, the CSS version is created automatically (which is handy for anyone willing to develop with LESS but don't want to rely on JavaScript on the client-side).

Gridpak is an interactive web application for generating responsive grid layouts very quickly.

The width of the grid, number of columns, column padding and gutter width can all be defined which are standard features we have seen from several other layout generators.

It gets better with the ability of adding breakpoints for responsive outputs. You can change the size of the layout, click "Add break point" and there you have it.

Once you have setup the layout, a custom download is ready which includes:

• a CSS file with all the classes and properties you need to create the responsive grid layout
• a LESS file with much the same information but including variables, mixins and methods to help you.
• an SCSS file like the LESS file, but in SCSS.
• a semi transparent PNG image for each grid you have created to help with your design, or with lining things up in your front end.
• a JavaScript snippet that allows you to toggle an overlay of your grid on and off in any browser using the 'G' key.

LESS is a great language for writing styles faster and getting more out of CSS with its dynamic nature (variables, mixins, operations and functions).

Normally, .less files are live-converted to CSS via JavaScript by the browser (or server -like Node.js-).

SimpLESS brings another option for designers willing to generate the CSS from .less files quickly.

It is a desktop-app that has versions for Windows, Mac OS X + Linux and works simply by drag 'n' dropping your project files into the app and getting the CSS output.

P.S. SimpLESS is also an open source project.

The Semantic Grid System is a fresh approach to CSS grids which allows us to define column-gutter widths, choose the number of columns and switch between pixels and percentages. And all these without the -kinda ugly- .grid_x classes used in the markup

It is built by Tyler Tate, the developer of the popular 1KB Grid and powered by Less.js (the dynamic stylesheet language).

The grid system is responsive as well and manipulating it using media queries is very easy.

There is also a detailed introduction of Semantic.gs in Smashing Magazine that is written by the developer himself.

BoxJS and BoxCSS are two different-yet-similar services built by the same developer team which offer a simplified method in compressing JavaScript and CSS files, serving the minimized versions and caching them.

They are free-to-use web apps which BoxJS requires including a lightweight JavaScript file (1.4kb) in web pages, specifying the JS files with a simple function and the service returns the minified + combined (into a single file) JavaScript file.

BoxCSS works by using the service's URL as the source of the CSS file but passing the original file's location as a querystring parameter.

Besides JavaScript and CSS, CoffeeScript and LESS is supported as well.

The drawback can be the need of relying to the CDN used by the services. In this case, you can use the service as a minifier and use the processes source file.