Libxml2 is the XML C library developed for the Gnome project. The library code is portable (to Linux, Unix, Windows, embedded systems, etc.) and modular; most of the extensions can be compiled out. Libxml2 implements a number of existing standards related to markup languages, including the XML standard, Namespaces in XML, XML Base, Relax NG, RFC 2396, XPath, XPointer, HTML4, XInclude, SGML Catalogs, and XML Catalogs. In most cases, libxml tries to implement the specifications in a relatively strict way. To some extent, it provides support for the following specifications, but doesn't claim to implement them: DOM, FTP client, HTTP client, and SAX2. Support for W3C XML Schemas is in progress. It includes xmllint, a command line XML validator.
Libxslt is a C library for GNOME which allows developers to work with XSLT. It is based on libxml for XML parsing, tree manipulation, and XPath support. Also included is 'xsltproc', a command line XSLT processor. The library is written in plain C, making as few assumptions as possible, and sticking closely to ANSI C/POSIX for easy embedding. It should work on Linux, Unix, and Windows. Though not designed primarily with performances in mind, libxslt seems to be a relatively fast processor. It also include full support for the EXSLT set of extension functions as well as some common extensions present in other XSLT engines.
htmLawed is a PHP script that makes input text more secure, HTML standards-compliant, and suitable in general from the viewpoint of a Web-page administrator, for use in the body of HTML 4 or XHTML 1 or 1.1 documents. It is a customizable HTML/XHTML filter, processor, purifier, and sanitizer. It can ensure that HTML tags are balanced and properly nested tags, neutralize code that may be used for cross-site scripting (XSS) attacks, and limit the allowed HTML elements, tags, attributes, or URL protocols.
Silva is a CMS for organizations that manage multiple or complex Web sites. Content is stored in clean XML, independent of layout and presentation. Features include versioning, a workflow system, an integral visual editor, content reuse, sophisticated access control, multi-site management, extensive import/export facilities, fine-grained templating, and hi-res image storage and manipulation. Silva is built on top of the Zope Web application platform.
htmlArea is a free WYSIWYG editor replacement for common textarea fields in HTML forms. Users can change the font size/color, make it bold/italicized/underlined, add bullets and numbering, insert images and links, and more. It works with any server-side software that accepts forms, including PHP, ASP, Perl, etc., and enables users to format their content as easily as if they were using a word processor. No HTML knowledge is required. Once the form is submitted, the raw HTML is passed along through your CGI script for use in your program.
GeSHi is a generic syntax highlighter for PHP that takes any source code and highlights it in XHTML and CSS. It features case-sensitive or insensitive highlighting, auto-caps/non-caps of any keyword, an unlimited scope for styling, the use of CSS in which almost any aspect of the source can be highlighted, the use of CSS classes to massively reduce the amount of output code, function-to-URL capabilities, line numbering, and much more. Over 100 languages are supported, including Java, C, PHP, HTML, CSS, SQL, Pascal, C++, XML, ASP, and ASM.
txt2html is a Perl program that uses the HTML::TextToHTML perl module to convert plain text to HTML. It supports headings, lists, tables, simple character markup, hyperlinking and is highly customizable. It recognizes some of the apparent structure of the source document (mostly whitespace and typographic layout) and attempts to mark that structure explicitly using HTML.