Windows. Includes validator, image scanner, meta tag manager, find and replace tool, tag pair fixer, and an HTML to text converter. Commercial software; 30-day demo.
Windows. Removes unnecessary characters from HTML, CSS, Perl, JavaScript and many other web file formats. Commercial pro version and free light version.
Windows and Unix. Object-oriented toolkit for SGML parsing and entity management. Can validate any version of HTML for which a DTD is available. Free Software.