Alex Shinn's Chibi-scheme is a r7rs "small" language compatible Scheme. It can be used standalone for scripting or as a library to provide an extension language. Full guide at http://synthcode.com/scheme/chibi/
Installation: hget http://chibi-scheme.googlecode.com/files/chibi-scheme-0.5.1.tgz | \ gunzip | tar xv cd chibi-scheme-0.5.1 mk install Its plan9 support needs more work: access to more of plan9 API, mkfile needs work + targets for .a, html docs, more tests, etc. but the port is eminently usable.
