LyX is a document processor that encourages an approach to writing based on the structure of your documents, not their appearance. It is intended for people people who write and want their writing to look great without tinkering with formatting details, font attributes, or page boundaries. On screen, it looks like any word processor, but it uses the TeX engine for printed output and producing richly cross-referenced PDFs. It is stable and fully featured.
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.
Txt2tags converts a text file with minimal markup to HTML, XHTML, SGML, DocBook, LaTeX, Lout, Man page, Creole, Wikipedia, Google Code Wiki, PmWiki, DokuWiki, MoinMoin, MagicPoint, PageMaker, AsciiDoc, or ASCII Art. It is simple and fast and features automatic TOC, macros, filters, include, tools, GUI, CLI, and Web interfaces, translations, and extensive documentation.
4Suite is a Python-based toolkit for XML and RDF application development. It features a library of integrated tools for XML processing, implementing open technologies such as DOM, RDF, XSLT, XInclude, XPointer, XLink, XPath, XUpdate, RELAX NG, and XML/SGML Catalogs. Layered upon this is an XML and RDF data repository and server, which supports multiple methods of data access, query, indexing, transformation, rich linking, and rule processing, and provides the data infrastructure of a full database system, including transactions, concurrency, access control, and management tools. It also supports HTTP, RPC, SOAP, and FTP, plus APIs in Python and XSLT.
doclifter helps with lifting documents with nroff markup to XML-DocBook. Lifting documents from presentation level to semantic level is hard, and a really good job requires human polishing. This tool aims to do everything that can be mechanized, and to preserve any troff-level information that might have structural implications in XML comments. TBL tables are translated into DocBook table markup, PIC into SVG, and EQN into MathML (relying on pic2svg and GNU eqn for the last two).
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.
Syntext Serna is a highly customizable, multi-platform, pure XSL-driven WYSIWYG XML content editor. It looks and works like a conventional word processor, yet it gives you much more flexibility to alter or reuse content while keeping its integrity intact. It lets you collaborate on compound documents that contain embedded data from various sources. Content is viewed as an integrated whole that is intuitively transparent to authors.