GNU TeXmacs is a free wysiwyw (what you see is what you want) editing platform with special features for scientists. The software aims to provide a unified and user friendly framework for editing structured documents with different types of content: text, mathematics, graphics, interactive content. TeXmacs can also be used as an interface to many external systems for computer algebra, numerical analysis, and statistics. New presentation styles can be written by the user and new features can be added to the editor using Scheme.
make_faq is an HTML generator that builds chunks/chapters/questions-and-answers or whatever, and builds indexes to hold it all together. It's a fairly general purpose tool for creating a set of indexed pages, but it's common usage is to build FAQ (Frequently Asked Questions) HTML from text documents. See the examples for a better understanding.
rpl is a Unix text replacement utility. It will replace strings with new strings in multiple text files. It can scan directories recursively and replace strings in all files found. The search can be limited to files with certain filename suffixes (e.g. '.html', '.c', etc.). It includes source, a build script, and a man page. It should work on most flavors of Unix. Linux/Intel, Linux/PPC, and source RPMs are available, as are binaries for other OSes, including Mac OS X.
Rute (Rute Users Tutorial and Exposition) is a book on GNU/Linux that aims to be the definitive guide for new users as well as sufficing as training course material, covering both the RHCE and LPI requirements. It covers essential theory to UNIX as well as giving practical tutorials on all fundamental aspects of Unix administration, from basic commands, the theory of TCP/IP, the Linux filesystem, through to configuration of mail, DNS, and other servers, through hardware configuration and package management. It is not Unix-specific but tends to give examples suited to Debian and RedHat-like systems. Rute comes in HTML and PDF formats.
Site Index is a simple script which generates HTML pages showing a site index for all of your local domains. It uses the natural hierarchy of your filesystem, so if you've organized your pages well, the job is fully automated. It breaks the index into multiple pages to respect a links-per-page limit, and can do some sorting/management of the results according to domain/page "importance".
The Kawa Scheme System is a full Scheme implementation, completely written in Java. Scheme functions and files are automatically compiled into Java byte-codes. Kawa does some optimizations, and the compiled code runs at a reasonable speed. It provides the usual read-eval-print loop, as well as batch modes. The Kawa compilation framework is also useful for implementing other languages on top of JVM. There is active development of XQuery (the XML query language), and less active development of Emacs Lisp, Common Lisp, and EcmaScript.