This is a great online equation editor. You enter a Latex string (with helper buttons to help you build the equation). Then you can download image to your web site. Amazing!

Open source image editing software:

Quoted: GIMP is the GNU Image Manipulation Program. It is a freely distributed piece of software for such tasks as photo retouching, image composition and image authoring.

The latest version of Dreamweaver is $399 retail.

Quoted: The official home of Adobe Dreamweaver CS3 (formerly Macromedia Dreamweaver 8), the industry leading web design and development tool. Buy or download free trial.

A WYSIWYG HTML editor (free). Zach likes it. Looks pretty decent - I haven't tried yet for anything "serious".

Quoted: HomeSite 5.5 provides a lean, code-only editor for web development. Advanced coding features enable you to instantly create and modify HTML, CFML, JSP, and XHTML tags, while enhanced productivity tools allow you to validate, reuse, navigate, and format code more easily. Configure Macromedia HomeSite to fit your needs by extending its functionality and customizing the interface.

Quoted: TopStyle is a powerful tool for creating standards-compliant Web sites. Written by the creator of HomeSite, TopStyle is a single editor for CSS, HTML and xHTML.

Quoted: HTML Kit is a free, full-featured, customizable, multi-purpose editor designed to help HTML, XHTML and XML authors to create and publish web pages. Newcomers can benefit from letting it point out errors and provide suggestions on how to create sta...

Add two lines of JavaScript to integrate this rich text editor into your web page.

Comparison of different rich text editors for Drupal. TinyMCE and FCKeditor seem to be the most popular.