KompoZer is a complete web authoring system that combines web file management and easy-to-use WYSIWYG web page editing.
KompoZer is designed to be extremely easy to use, making it ideal for non-technical computer users who want to create an attractive, professional-looking web site without needing to know HTML or web coding.

http://kompozer.net

NVU - Finally! A complete Web Authoring System for Linux Desktop, Microsoft Windows and Macintosh users to rival programs like FrontPage and Dreamweaver. Nvu (pronounced N-view, for a "new view") makes managing a web site a snap. Now anyone can create web pages and manage a website with no technical expertise or knowledge of HTML.

http://www.nvu.com

Quanta Plus is a highly stable and feature rich web development environment. The vision with Quanta has always been to start with the best architectural foundations, design for efficient and natural use and enable maximal user extensibility. We recognize that we don't have the resources to do everything we would like to so our target is to make it easy for you to help make this the best community based desktop application anywhere. Pretty much everything in Quanta is designed so you can extend it. Even the way it handles XML DTDs is based on XML files you can edit. You can even import DTDs, write scripts to manage editor contents, visually create dialogs for your scripts and assign script actions to nearly any file operation in a project. You can even look at and communicate with a wide range of what happens inside Quanta using DCOP. 

http://quanta.kdewebdev.org/

Web-browser, advanced e-mail and newsgroup client, IRC chat client, and HTML editing made simple -- all your Internet needs in one application. 

http://www.seamonkey-project.org/