Gambit consists of two main programs: gsi, the Gambit Scheme interpreter, and gsc, the Gambit Scheme compiler. The interpreter contains the complete execution and debugging environment. The compiler is the interpreter extended with the capability of generating executable files. The compiler can produce standalone executables or compiled modules which can be loaded at run time. Interpreted code and compiled code can be freely mixed.

String pattern-matching library for scheme48 based on the SRE regular-expression notation.

GNU/MIT Scheme is an implementation of the Scheme programming language. It provides an interpreter, a compiler and a debugger. It also features an integrated Emacs-like editor and a large runtime library.

HOP is a multi-tier programming language for the Web 2.0 and the so-called diffuse Web. It is designed for programming interactive web applications in many fields such as multimedia (web galleries, music players, ...), ubiquitous and house automation (SmartPhones, personal appliance), mashups, office (web agendas, mail clients, ...), etc.

Loko Scheme is intended to be a platform for application and operating system development. It is written purely in Scheme and some assembler (i.e. no C code at the bottom). Both the R6RS and the R7RS standards are supported.

TinyScheme is a light-weight Scheme interpreter that implements as large a subset of R5RS as was possible without getting very large and complicated.

It's meant to be used as an embedded scripting interpreter for other programs. As such, it does not offer an Integrated Development Environment (IDE) or extensive toolkits, although it does sport a small (and optional) top-level loop.

As an embedded interpreter, it allows multiple interpreter states to coexist in the same program, without any interference between them. Foreign functions in C can be added and values can be defined in the Scheme environment. Being quite a small program, it is easy to comprehend, get to grips with, and use.

Pre-Scheme is a statically compilable dialect of Scheme, used to implement the Scheme 48 virtual machine. Scheme 48 ships with a Pre-Scheme to C compiler written in Scheme, and a runtime library which allows Pre-Scheme code to run as Scheme.

This is a R7RS Scheme implementation designed to run within a Common Lisp environment.

Gerbil is an opinionated dialect of Scheme designed for Systems Programming, with a state of the art macro and module system on top of the Gambit runtime. The macro system is based on quote-syntax, and provides the full meta-syntactic tower with a native implementation of syntax-case. It also provides a full-blown module system, similar to PLT Scheme's (sorry, Racket) modules. The main difference from Racket is that Gerbil modules are single instantiation, supporting high performance ahead of time compilation and compiled macros.

This is a R7RS Scheme implementation designed to run within a Common Lisp environment.

Gerbil mode provides font-lock, indentation, navigation, and REPL for Gerbil code within Emacs.

Chibi-Scheme is a very small library with no external dependencies intended for use as an extension and scripting language in C programs. In addition to support for lightweight VM-based threads, each VM itself runs in an isolated heap allowing multiple VMs to run simultaneously in different OS threads.

Stalin is an aggressively optimizing whole-program compiler for Scheme that does polyvariant interprocedural flow analysis, flow-directed interprocedural escape analysis, flow-directed lightweight CPS conversion, flow-directed lightweight closure conversion, flow-directed interprocedural lifetime analysis, automatic in-lining, unboxing, and flow-directed program-specific and program-point-specific low-level representation selection and code generation.

GNU SCM is an implementation of Scheme. This implementation includes Hobbit, a Scheme-to-C compiler, which can generate C files whose binaries can be dynamically or statically linked with a SCM executable.

Revised^7 Report of the Algorithmic Language Scheme adapted to Texinfo format.

SLIB is a portable Scheme library providing compatibility and utility functions for all standard Scheme implementations.

Unsyntax is an implementation of the Scheme programming language, specifically of its R7RS standard, and includes a number of extensions. Unsyntax evaluates Scheme expressions and compiles and runs Scheme programs by first expanding them into a minimal dialect of R7RS (small) without any syntactic extensions. The resulting expression or program is then evaluated by an existing Scheme implementation.

Bigloo is a Scheme implementation devoted to one goal: enabling Scheme based programming style where C(++) is usually required. Bigloo attempts to make Scheme practical by offering features usually presented by traditional programming languages but not offered by Scheme and functional programming. Bigloo compiles Scheme modules. It delivers small and fast stand alone binary executables. Bigloo enables full connections between Scheme and C programs and between Scheme and Java programs.

STklos is a free Scheme system mostly compliant with the languages features defined in R7RS small. The aim of this implementation is to be fast as well as light. The implementation is based on an ad-hoc Virtual Machine. STklos can also be compiled as a library and embedded in an application.

TR7 is a lightweight Scheme interpreter that implements the revision R7RS small of scheme programming language.

It is meant to be used as an embedded scripting interpreter for other programs. A lot of functionality in TR7 is included conditionally, to allow developers freedom in balancing features and footprint.

Scheme 48 is an implementation of Scheme based on a byte-code interpreter and is designed to be used as a testbed for experiments in implementation techniques and as an expository tool.

Gauche is a R7RS Scheme scripting engine aiming at being a handy tool that helps programmers and system administrators to write small to large scripts quickly. Quick startup, built-in system interface, native multilingual support are some of the goals. Gauche comes with a package manager/installer gauche-package which can download, compile, install and list gauche extension packages.

Owl Lisp is a simple programming language. It is intended to provide a portable system for writing standalone programs in a subjectively pleasant dialect of Lisp. It has a minimal core and runtime, purely functional operation, and support for asynchronous evaluation.

Scheme 9 from Empty Space (S9fES) is a mature, portable, and comprehensible public-domain interpreter for R4RS Scheme offering:

• bignum arithmetics

• decimal-based real number arithmetics

• support for low-level Unix programming

• cursor addressing with Curses

• basic networking procedures

• an integrated online help system

• loads of useful library functions