Wordoff applies the following rules to strip the cruft that is pasted into WYSIWYG editors from Word:
Attributes are removed for all elements except ss and s are removedEmpty elements are removedConsecutive line breaks are reduced to two
HTML Purifier is a standards-compliant HTML filter library written in PHP. HTML Purifier will not only remove all malicious code (better known as XSS) with a thoroughly audited, secure yet permissive whitelist, it will also make sure your documents are standards compliant, something only achievable with a comprehensive knowledge of W3C's specifications. Tired of using BBCode due to the current landscape of deficient or insecure HTML filters? Have a WYSIWYG editor but never been able to use it? Looking for high-quality, standards-compliant, open-source components for that application you're building? HTML Purifier is for you!
2008-06-19 Skybound offers a free version of Stylizer Basic (formerly StyleSpread) in addition to the non-free Stylizer Ultimate. Stylizer is a CSS editor with live preview, automatic validation, diagnose tool, FTP upload, etc. (Windows, free basic version)
Construct is a visual layout editor based on Blueprint & jQuery! This is version 0.5, last updated on April 27, 2008. This project was built by Christian Montoya, and exists both as a useful tool for CSS designers and as proof that a visual layout editor is possible to acheive with clean CSS & semantic HTML.