GNU Guile 2.1.1 released [beta]

Guile is an implementation of the Scheme programming language, with
support for many SRFIs, packaged for use in a wide variety of
environments.  In addition to implementing the R5RS Scheme standard,
Guile includes a module system, full access to POSIX system calls,
networking support, multiple threads, dynamic linking, a foreign
function call interface, and powerful string processing.

Guile can run interactively, as a script interpreter, and as a Scheme
compiler to VM bytecode.