FarsiTeX
Free Persian/English bidirectional typesetting system based on TeX. Currently available only for DOS. You Would also find info related to Farsi, Persian, FarsiTeX, Desktop Publishing, Typesetting, LaTeX, TeX, METAFONT, XML, PDF and much more.

NTS
The NTS projected is aimed at developing successor for TeX; a New Typesetting System.

PDFTeX
A version of TeX that produces PDFs instead of DVIs. You Would also find info related to TeX, PDF, typesetting and much more.

TeX++
A modern and free C++ implementation of TeX based on CommonTeX.

e-TeX
e-TeX tries to extend TeX while staying completely compatible to TeX.

HyperTeX
A standard of \specials for turning (La)TeX documents in hyperdocuments supported by previewers for DVI and Postscript files.

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.

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.

TeX in C
Project converting the TeX source code from Web to C. Download of code and information on the conversion.

TeXlib
A SourceForge project to develop a run-time TeX library, with support for enhancements such as e-TeX, pdf-e-TeX, Omega.