Optimizer/Formatter

• CSSTidy - CSS Tidy is an open source CSS parser and optimiser.
• CleanCSS - CleanCSS is a powerful CSS optimizer and formatter. Based on CSSTidy
• CSS Optimizer - CSS Optimizer reduces the file size of cascading style sheets.
• CSS Analyzer - CSS Analyzer allows you to check the validity of your CSS against the W3C’s validation service

Font

• Em Calculator - EM Calculator calculats pixel font sizes to ems.
• CSS Font and Text Style Wizard - This wizard is good to experiment with font and text styles and generate sample CSS style source code.

Forms

• CSS Form Code Maker - Generates ‘Colorful Box Layout’ For Forms
• JotForm - JotForm is a web based WYSIWYG form builder

Navigation/Buttons

• CSS Buttons - Css Button and Text field Generator.
• CSS Menu Generator - CSS Menu Generator will generate both the CSS and the HTML code required to produce a text-based yet appealing set of navigation buttons.

Generator

• CSS Creator - Css Creator is a layout generator that will create a fluid or fixed width floated column layout, with up to 3 columns and with header and footer.
• QrONE CSS Designer - QrONE is an online CSS generator and editor.
• Web 2.0 Generator - Web 2.0 Generator creates a full website layout with HTML and CSS.
• CSS Mate - CSS Mate is an online CSS editor.

• - Blueprint CSS framework created by Olav Bjorkoy is a framework that offers an easily customizable grid, sensible typography, and even a stylesheet for printing. A lot of the CSS in this project is completely based on work by other people, like: Jeff Croft , Nathan Borror, Christian Metts, and Eric Meyer. The Blueprint CSS Framework is available for use in all personal or commercial projects, under both the MIT and the GPL license.
• - YAML aka “Yet Another Multicolumn Layout”, is an (X)HTML/CSS framework for creating modern and flexible floated layouts. YAML created by Dirk Jesse fully supports all IE versions. The YAML framework is published under the Creative Commons Attribution 2.0 License, which permits both private and commercial use. YAML is also very flexible and comes with a bilingual documentation. YAML even has a layout/css builder, that allows visual configuration of the basic layout elements, that is very cool.
• - 960 Grid System created by Nathan Smith is a CSS framework for grids. The 960 Grid System’s purpose is to streamline web development workflow by providing commonly used dimensions, based on a width of 960 pixels. The reason for 960 pixels is because 960 is divisible by 2, 3, 4, 5, 6, 8, 10, 12, 15, 16, 20, 24, 30, 32, 40, 48, 60, 64, 80, 96, 120, 160, 192, 240, 320 and 480. This makes it a highly flexible base number to work with.
• UI Grid CSS - The entire YUI CSS foundation includes the Reset, Fonts, and Grids packages. It even contains a grid builder to allow for faster development. The Yahoo! UI Grid CSS supports easy customization of the width for fixed-width layouts.
• - Logic CSS framework is a collection of CSS files and PHP utilities to cut development times for web-standards compliant xHTML layouts.
• - ESWAT is web project framework kit that contains a folder structure and some pre-written components. The ESWAT framework is meant to remove the hassle of recreating the same folders, HTML tags, CSS rules, Photoshop guides, etc.
• - Elements is a CSS Framework that was developed by Ben Henschel. It lets you write CSS easier, faster, more efficient, and allows you to organize all of your project files. Elements goes beyond being just a framework, it’s its own project workflow.

YUI CSS库
http://developer.yahoo.com/yui/

YAML（Yet Another Multicolumn Layout）
http://www.yaml.de/en/

Content with Style: A CSS Framework
http://www.contentwithstyle.co.uk/Articles/17/

Blueprint
http://code.google.com/p/blueprintcss/

tripoli
http://monc.se/tripoli/

Elements
http://elements.projectdesigns.org/index.html

WYMstyle: a CSS framework
http://www.wymstyle.org/en/

taffy-css-framework
http://code.google.com/p/taffy-css-framework/

See Also:
CSS Framework CSS框架入门教程
blueprint--css framework研究
理解Web框架，和如何构建一个CSS框架

下面列出十几个网上可见的HTML编辑器：