I noticed a different kind of WYSIWYG editor today (credits to Brian R) called WYMeditor. It strives to provide an easy-to-use content editor for non-technical users, while keeping the formatting options to a minimum. It's actually dubbed as a WYSIWYM (what you see is what you mean) editor, and outputs XHTML for easy insertion into CMS systems. Plus, it's open source, and very lightweight. 

Their words:

WYMeditor's main concept is to leave details of the document's visual layout, and to concentrate on its structure and meaning, while trying to give the user as much comfort as possible (at least as WYSIWYG editors).

I like the idea behind WYMeditor, because it strives to avoid my beefs with many existing content editors:

• Many common WYSIWYG editors allow too much control over the content, allow users to paste in horribly-mangled HTML from Word, etc., and/or output HTML that's laden with inline styles, extra formatting (extra breaks, tables, non-breaking spaces), and not XHTML. The content often "looks ok" in the editor, but then doesn't work out well in the site. Or, the layout can get "messed up" in the editor, but since the user doesn't look at or understand the underlying HTML, he or she isn't able to fix the formatting issue without deleting all the content and trying again. Lastly, trying to clean up the editor's HTML output & insert it into an existing page template can be tricky and leave you with a funny-looking page.
• The other direction, using a text-only editor with special characters for formatting (like many wikis do) minimizes problematic formatting, but is less natural to non-technical users who are expecting something to "look like Microsoft Word." And I don't blame them -- Alan Cooper wrote in one of his books about how often programmers forget to design interfaces that work the way users are used or and/or expect them to, and how that can cause unexpected usability issues or other problems. Not that we should never offer anything new to users with old habits, but...well you know what I'm getting at.

However, WYMeditor is still young, barebones, & has its share of issues (no nested lists, certain browser compatibility, trouble deleting HTML tables, etc). Still, WYMeditor might be a good option now or in the future, depending on your audience and application.