Scwm is the Scheme Constraints Window Manager, a highly dynamic and extensible window manager for the X Window System. Scwm embeds Guile Scheme as the configuration and extension language, and includes a sophisticated constraint solver for permitting the user to interactively specify constraints among top-level window sizes and positions. Nearly all decorations can be changed at runtime on a per-window basis. Dynamic loading of C modules is supported. Scwm is self-documenting and provides a powerful protocol for interacting with the window manager from other processes.
Serveez is a server framework which provides routines and help for implementing IP-based servers (TCP, UDP, and ICMP). It is also possible to use named pipes for all connection-oriented protocols. The package includes a number of servers that work already: an HTTP server, an IRC server, a Gnutella spider, and some others. One of the highlights is that you can run all protocols on the same port. The application itself is single-threaded, but it uses helper processes for concurrent name resolution and ident lookups.
Siag Office is a free office package which consists of the spreadsheet Siag, the word processor PW, the animation program Egon, the text editor XedPlus, the file manager Xfiler and the previewer Gvu. Siag is easy to use, yet infinitely flexible through multiple embedded interpreters and a plugin mechanism that allows other programs to run inside the main document. The supported interpreters are SIOD, Guile, Tcl, and Python.
SISC is an extensible Java-based interpreter of the algorithmic language Scheme. It uses modern interpretation techniques and handily outperforms all existing Java interpreters (often by more than an order of magnitude). In addition, SISC is a complete implementation of the language. The entire R5RS Scheme standard is supported. This includes a full number tower including complex number support and arbitrary precision integers and floating point numbers, proper tail recursion, hygienic macros, and full support for first-class continuations (not just the escaping continuations found in many other systems).
Sizzle is a Scheme interpreter for embedding into C applications and for standalone scripting. It implements a nearly complete subset of R5RS Scheme, adding a lot of primitives for U*ix scripting, regular expression searching, a simple module system, dynamic library linking, powerful string processing procedures, and much more. It includes a user's guide and an embedding manual in texinfo format, some examples, the embedding library, and a standalone interpreter for interactive use and scripting.
STklos is a free Scheme System conforming to R5RS. The implementation is based on an ad-hoc Virtual Machine. It can also be compiled as a library, so that one can easily embed it in an application. Its features include an efficient and powerful object system based on CLOS, a simple-to-use module system, implementation of the full tower of numbers defined in R5RS, and easy connection to the GTK+ toolkit. STklos is the successor of STk, a Scheme interpreter tightly connected to the Tk toolkit.
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.
TinyScheme is a lightweight Scheme interpreter that implements as large a subset of R5RS as possible without getting very large and complicated. It is meant to be used as an embedded scripting interpreter for other programs. As such, it does not offer IDEs or extensive toolkits although it does sport a small top-level loop, included conditionally. A lot of functionality in TinyScheme is included conditionally, and it allows multiple interpreter states to coexist in the same program without any interference between them. Foreign functions in C can also be added and values can be defined in the Scheme environment.
GNU Radius is a RADIUS server and an accompanying set of monitoring utilities. It features MySQL and PostgreSQL interfaces for authentication and/or logging (the ODBC interface allows you to use almost any existing DBMS for that purpose), the ability to rewrite RADIUS requests from various NASs to normalize them to a more understandable format, and the ability to completely customize the behavior of RADIUS authentication and accounting based on NAS and user attributes.