Bigloo is an implementation of the Scheme programming language. It relies on an optimizing compiler from Scheme to C. Bigloo enables connections between Scheme code and C code. It proposes many extensions to Scheme such as a regular parser compiler, an lalr parser compiler, pattern matching, an object layer, etc.
mu is a collection of utilities for maildirs, in particular for indexing and searching them. mu fills a database with information about your emails, which can then be queried using an easy query language. It can work stand-alone or be integrated with a mail client. It also provides an emacs-based email client ("mu4e") and bindings for Guile/Scheme.
Chicken is a Scheme compiler that translates most of R5RS Scheme into relatively portable C. It supports fully general tail-call recursion, first-class continuations, and has a very flexible and efficient interface to C and C++. Chicken implements several extensions to the Scheme language: lightweight threads, pattern matching macros, dynamic loading of compiled code, and various object-oriented paradigms, such as TinyCLOS, and others. The library system includes hundreds of convenient modules for practical use.
InteLib is a library of C++ classes that lets you do Lisp/Scheme programming within your C++ programs, even without any additional preprocessing, without all those calling conventions. You can write code that is accepted by a C++ compiler while thinking in a "Lisp/Scheme mode", and the code you write will look much like Lisp/Scheme code, although it will be pure C++.
Meep is a free finite-difference time-domain (FDTD) simulation software package to model electromagnetic systems. It supports distributed-memory parallel simulations, nonlinear, anisotropic, and dispersive media, PML absorbing boundaries, and 1D/2D/3D and cylindrical problems. It is completely scriptable from either C++ or a Scheme (GNU Guile) interface.
libtour is a generic tournament processing library. The rules, participants, schedule, and results of a sporting tournament can be defined in the Scheme programming language and given to the library as input. A CLI application is provided as a reference client implementation. See http://freshmeat.net/projects/qtour/ for a Qt-based client.
Kahua is a continuation passing style (CPS) application framework and server. It is written using the Gauche implementation of Scheme. It has the advantage that you can use "continuations" easily, so you can solve the typical Web application's problem of process disconnection. It allows you to program declaratively by using S-expressions as a fundamental data type, you can use Kahua's Object Database to persist data, and you can modify the function being run, supporting incremental development.
travtrack is a tool to help a Traveller(tm) referee keep track of essential data for a game. Already implemented are galaxies, sectors, subsectors, systems, stars, planets, belt and moons. Yet to be implemented are trade routes, ships, characters, and all the rest. These will take some time, but should not be too complex. It currently uses the GURPS Traveller:First In rules for system generation, but a subproject is under way to add Classic Traveller generation and output. travlib is a collection of C routines that should make writing a Traveller application easier. A guile interface to the data representation functions is provided.
MzVim is the Vim editor with an embedded MzScheme interpreter. MzScheme is a lightweight, embeddable, scripting-friendly PLT Scheme implementation. It provides full access to Vim commands and registers, and to VimL built-in variables and functions, so there is no need to execute Vim statements in string literal form. It also features OS-independent threads and an event-handling mechanism which allows Scheme to be used for autocommands, keyboard mappings, and menus.