Tools

Astyle CSS Editor
Windows based editor with a 30 day trial period.
http://www.athlab.com

Back To Font
Stylesheet color picker for background and fonts. Written in Javascript.
http://www.markup.co.nz/colorPicker/back_to_font_home.htm

Cascades
Stylesheet editor for Composer, the HTML editor of Mozilla/Netscape. [Freeware]
http://cascades.mozdev.org/

Clean CSS
An online CSS formatter and optimiser. Enter CSS code, select from a range of options, and receive the cleaned output.
http://www.cleancss.com/

CoffeeCup StyleSheet Maker
Allows users to construct full-featured cascading style sheets. [Shareware]
http://www.coffeecup.com/stylesheet-maker/

CSS Compressor
Online tool to compress CSS code for faster downloads. Includes various options.
http://iceyboard.no-ip.org/projects/css_compressor

CSS Mate
Free browser based CSS editor. Tested on Firefox and MS IExplorer.
http://cssmate.com

CSS Menu Generator
Generates CSS HTML code for a text-based navigation buttons.
http://www.webmaster-toolkit.com/css-menu-generator.shtml

CSS Optimiser
Online CSS optimizer, for reducing the file size of cascading style sheets.
http://www.cssoptimiser.com

CSS Organizer
Use this tool to reorganize your CSS online. Simply submit your cascading style sheet, and receive the suggested reorganization.
http://www.lonniebest.com/FormatCSS/

CSS Template Generator
Generates a 3-column layout without tables.
http://www.ibdjohn.com/csstemplate/

CSSED
A GTK2 application to help create and maintain CSS style sheets for web developing. An open source project.
http://cssed.sourceforge.net/

CSSEZ
Online tools to provide customized CSS examples for blog systems.
http://www.cssez.com/

CSSTidy
Open source CSS parser and optimiser. Downloads, documentation, and developer information.
http://csstidy.sourceforge.net/

DeCSS
A utility for stripping CSS tags from an HTML page.
http://www.pigdog.org/decss/

Dynamic Drive: Style Sheet Switcher
A "plug and play" style sheet switcher that lets visitors switch between a list of alternative style sheets to apply to your site. Uses cookies for persistence.
http://www.dynamicdrive.com/dynamicindex9/stylesheetswitcher.htm

Flumpcakes: Online CSS Optimizer
This tool reads CSS just like a browser would. So using hacks which are browser specific will give random results, make sure any hacks are removed before use.
http://flumpcakes.co.uk/css/optimiser/

Pixy: CSS Editor
Beta/ demo of an online CSS editor. Free to use.
http://www.pixy.cz/apps/webedit/

Rapid CSS Editor
HTML and style sheet editor for Windows. [Shareware]
http://www.blumentals.net/rapidcss/

RichInStyle MySite
Allows users to select a style sheet or create a custom one to view the site.
http://www.richinstyle.com/free/mysite.html

Scriptomizers
Generates cascading stylesheets via web-based form.
http://www.scriptomizers.com/css/stylesheet_generator

Simple CSS
Style sheet creator for Macintosh and Windows. Supports CSS 2.0. By HostM.com. [Freeware]
http://www.hostm.com/css/

Sky CSS Tool
Online CSS authoring tool. Allows you to create CSS classes almost without using manuscript code. JavaScript compatible browser is needed for the proper functioning.
http://skycsstool.sourceforge.net/

Style Master
Style sheet editor for Windows and Macintosh. By Western Civilization Pty. Ltd. [Shareware]
http://www.westciv.com/style_master/

Style Studio
HTML and style sheets editor and validator for Windows.
http://www.highdots.com/css-editor/

TopStyle
HTML, XHTML, CSS Editor for Windows by the creator of HomeSite.
http://www.newsgator.com/Individuals/TopStyle/

Ulaska's CSS Creating Tool
Generate customized code for a page. Written in PHP, JavaScript, HTML and MySQL.
http://alla.ulaska.com/css/