» pdfTeX    An extended version of TeX that can create PDF directly from TeX source files and enhance the result of TeX typesetting with the help of PDF. When PDF output is not selected, pdfTeX produces normal DVI output.    http://www.tug.org/applications/pdftex/

» An \eval for TeX    Using Scheme as an extension language for TeX. Download, documentation and information about PicScheme.    http://www.ccs.neu.edu/home/dorai/tex2page/eval4tex-doc.html

» ExTeX    New TeX engine in development, written in Java and based on NTS, ε-TeX, pdfTeX, and Ω (Omega). Development information, documentation, mailing lists and download.    http://www.extex.org/

» FarsiTeX    Free Persian/English bidirectional typesetting system based on TeX. Currently available only for DOS.    http://www.farsitex.org/

» HyperTeX    A standard of \specials for turning (La)TeX documents in hyperdocuments supported by previewers for DVI and Postscript files.    http://arxiv.org/hypertex/

» LuaTeX    An extended version of pdfTeX using Lua as an embedded scripting language. Roadmap, FAQs, source code and documentation.    http://www.luatex.org/

» NTS    The NTS projected is aimed at developing successor for TeX; a New Typesetting System.    http://nts.tug.org/

» Omega Project    Omega is an extension of TeX developed by John Plaice (Université Laval, Canada) and Yannis Haralambous (Atelier Fluxus Virus, France) aimed primarily at improving TeX's multilingual abilities.    http://omega.enstb.org/

» PyTex    Python programming plus TeX typesetting. Information about the concept, documents and links to the SourceForge page with download and mailing list. Also home of Active TeX, a forerunner of PyTeX, and the TeX daemon.    http://www.pytex.org/

» QaTeX    Allows Python modules to be used instead of (La)TeX style files to ease La(TeX) programming.    http://qatex.sourceforge.net/

» TeX in C    Project converting the TeX source code from Web to C. Download of code and information on the conversion.    http://www.math.uni.wroc.pl/~hebisch/tex/

» TeX++    A modern and free C++ implementation of TeX based on CommonTeX.    http://www.aei.mpg.de/~peekas/tex++/

» TeXlib    A SourceForge project to develop a run-time TeX library, with support for enhancements such as e-TeX, pdf-e-TeX, Omega.    http://sourceforge.net/projects/texlib/

» easyLaTeX    Software which calls all tools necessary to create PDF, DVI or HTML output out of simple text files (via LaTeX) using LaTeX like syntax. Download and documentation.    http://www.8ung.at/easylatex/

» mimeTeX    Program licensed under the GNU GPL which parses LaTeX math expressions emitting images which can be used directly in HTML documents. Introduction, manual and download.    http://www.forkosh.dreamhost.com/cgi-bin/mimetexquickstart.cgi

» sTeXme    Allows to manipulate TeX internals using the Scheme programming language. Sourceforge project page and guides.    http://stexme.sourceforge.net/