actually a true programming language, provided with high level features (such as objects, higher order functions, regular and syntactic parsing, etc.). Scribe is based on the Scheme programming language
Schemik is a high-level lexically-scoped implicitly-parallel dialect of Scheme and Common LISP. This means the parallel execution of programs is done independently of the programmer, and each program written in Schemik always produces the same results no matter which parts of the program are executed simultaneously.
(commercial) follows the mainstream Prolog tradition in terms of syntax and built-in predicates. As of release 3.8, SICStus Prolog provides two execution modes: the iso mode, which is fully compliant with the International Standard ISO/IEC 13211-1 (PROLOG: Part 1--General Core); and the sicstus mode, which is largely compatible with e.g. C-Prolog and Quintus Prolog, supports code written in earlier versions of SICStus Prolog
a High Performance, Portable, Parallel Programming Language
Sizzle is an interpreter for the Scheme programming language. Sizzle is designed to be embedded into other applications as an extension language, but it can also be used as a standalone interpreter for interactive use and scripting.
Standard ML is a safe, modular, strict, functional, a polymorphic programming language with compile-time type checking and type inference, garbage collection, exception handling, immutable data types and updatable references, abstract data types, and parametric modules
a free Scheme System (nearly) conform to R5RS. 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, so that one can easily embed it in an application
a portable implementation of the Scheme Programming language. It conforms to IEEE/ANSI standard of Scheme and supports all features of the R5RS Report on Scheme. In addition, SXM supports numerous features of Chez Scheme v6.0 and SRFIs 0, 6, 8, 11, and 16
designed as an extended, Scheme-like language for Posix environments (especially Unix). Extended means that the language goes far beyond standard Scheme. Scheme-like means that Systas does not aim to be strictly conformant with standard scheme, although it is close enough to run some of my favorite SRFI packages
TL3 is a compact lisp interpretor that is an ancestor of Lush. It is pretty clean with a full online documentation, a graphic toolkit, an extension protocol, etc.