Librep is a shared library implementing a Lisp dialect that is lightweight, reasonably fast, and highly extensible. It contains an interpreter, byte-code compiler, and virtual machine. Applications may use the interpreter as an extension language, or it may be used for standalone scripts. Rep was originally inspired by Emacs Lisp. However one of the main deficiencies of elisp--the reliance on dynamic scope--has been removed. Also, rep only has a single namespace for symbols.
MDK (MIX Development Kit) provides tools for developing and executing, in a MIX virtual machine, MIXAL programs. The MIX is Donald Knuth's mythical computer, described in the first volume of The Art of Computer Programming, which is programmed using MIXAL, the MIX assembly language. MDK includes a MIXAL assembler (mixasm), a MIX virtual machine (mixvm) with a command line interface, a Guile-based virtual machine (mixguile), a GTK+ based GUI (gmixvm), and a mixvm-Emacs interface (mixvm.el). MDK utilities are extensible using Scheme.
OBJ3 is a program specification and proof system based on order sorted equational logic. It has been successfully used for research and teaching in software design and specification, rapid prototyping, theorem proving, user interface design, and hardware verification, among other things. It was the first language to implement parameterized programming and its module system influenced the designs of the Ada, C++, and ML module systems.
Steel Bank Common Lisp is a development environment for Common Lisp, with excellent support for the ANSI standard: garbage collection, lexical closures, powerful macros, strong dynamic typing, incremental compilation, and the famous Common Lisp Object System (multimethods and all). It also includes many extensions, such as native threads, socket support, a statistical profiler, programmable streams, and more. These are all available through an integrated, interactive native compiler which feels like an interpreter. SBCL is unique in being a multiplatform native compiler which bootstraps itself completely from source, using a C compiler and any other ANSI Common Lisp implementation.
Gamma is a dynamically-typed, object-oriented, interpreted programming language that has been designed and optimized to reduce the time required for building applications. It supports the QNX/Photon and Linux/GTK GUI environments, and has a built-in library of over 300 functions. It cuts development times and offers run-time debugging by wedding a C-like syntax to a Lisp interpreter that has been optimized specifically for performance and memory usage.