crypt++.el is a package of Lisp functions that recognize automatically encrypted and encoded (i.e., compressed) files when they are first visited or written. The BUFFER corresponding to the file is decoded and/or decrypted before it is presented to the user. The file itself is unchanged on the disk. When the buffer is subsequently saved to disk, a hook function re-encodes the buffer before the actual disk write takes place.
Eev.el is a simple Emacs Lisp library that lets you treat portions of a text file as shell commands, chunks of code for programming languages or as hyperlinks; its intention is to let people record into plain ASCII files their interaction with the computer, and to let them edit and play back any block of code in those files easily. The hyperlinks can point to places in manpages, Info pages and text or HTML files, and they are seen as comments by all programming languages; using them you can place pointers to all relevant online sources of information inside the code.
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.
Gnutran is a simple, Emacs-based front-end to a number of machine translation engines available on the Web. It can send emacs buffers to a translation engine, request a translation (e.g. English to Portuguese) and display the result on a new window. GNUTRAN interoperates with emacs-based email agents such as VM-Mail and features a highly configurable interface, allowing easy set up of new translation pairs through Emacs' customization interface.
ics.el is a comint based Emacs major mode for handling the text portion of communications with internet chess servers such as FICS and ICC. It is written in Emacs-Lisp and works best in conjunction with a graphical interface such as Xboard. It handles colour highlighting and "buttonisation" (making certain portions of text active so that, for example, you can challenge opponents with a single mouse click) as well as command recall and editing and automation of commands based on regexps seen in the ICS output, all highly customisable using Emacs lisp.
The Remembrance Agent (RA) watches your over your shoulder and continuously updates a list of documents relevant to what is being typed or read in an Emacs buffer. Suggestions are then displayed in their own window at the bottom of the frame, and are continually updated every few seconds. The RA uses a multi-field information-retrieval back-end called Savant that can index several different kinds of files, including email archives, HTML, LaTeX, and plain text format.
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.