Pixie is a lightweight lisp suitable for both general use as well as shell scripting. The standard library is heavily inspired by Clojure as well as several other functional programming languages. It is written in RPython and as such supports a fairly fast GC and an amazingly fast tracing JIT.
Ferret is a free software lisp implementation designed to be used in real time embedded control systems. Ferret lisp compiles down to self contained C++11. Generated code is portable between any Operating System and/or Microcontroller that supports a C++11 compliant compiler. It has been verified to run on architectures ranging from embedded systems with as little as 2KB of RAM to general purpose computers running Linux/Mac OS X/Windows.
Janet is a functional and imperative programming language. It runs on Windows, Linux, macOS, BSDs, and should run on other systems with some porting. The entire language (core library, interpreter, compiler, assembler, PEG) is less than 1MB. You can also add Janet scripting to an application by embedding a single C file and two headers.