Unsemantic is a fluid grid system that is the successor to the 960 Grid System. It works in a similar way, but instead of being a set number of columns, it’s entirely based on percentages.

Initializr is an HTML5 templates generator to help you getting started with a new project based on HTML5 Boilerplate. It generates for you a clean customizable template with just what you need to start!

Bootstrap is a toolkit from Twitter designed to kickstart development of webapps and sites. It includes base CSS and HTML for typography, forms, buttons, tables, grids, navigation, and more.

Dig responsive design? Hate fluid grids? Try a Frameless grid.

A unified user interface system across all popular mobile device platforms, built on the rock-solid jQuery and jQuery UI foundation. Its lightweight code is built with progressive enhancement, and has a flexible, easily themeable design.

Another collection of templates for HTML, CSS, and JavaScript.

Boilerplate might be the wrong word for this, but it’s incredibly thorough and is great as a reference.

A web grid system designed by Joseph Silvashy and New Gold Leaf that allows designers to use the screen real estate on large monitors and retain great design on smaller ones. The Fluid Grid System combines the principals of the typographic grid and a baseline grid into one resolution-independent framework.

Raphaël is a small JavaScript library that should simplify your work with vector graphics on the web. If you want to create your own specific chart or image crop and rotate widget, for example, you can achieve it simply and easily with this library.

The Closure tools help developers to build rich web applications with JavaScript that is both powerful and efficient.

Underscore is a utility-belt library for JavaScript that provides a lot of the functional programming support that you would expect in Prototype.js (or Ruby), but without extending any of the built-in JavaScript objects. It’s the tie to go along with jQuery’s tux.