Scheme 48 is an implementation of Scheme written by Richard Kelsey and Jonathan Rees. It is based on a byte-code interpreter and is designed to be used as a testbed for experiments in implementation techniques and as an expository tool.
The current version of Scheme 48 is 1.8 (released February 07, 2008).
Instructions for getting the current development sources and building them are here.
Scsh (SCheme SHell) is a scripting and systems programming environment built on top of Scheme 48 and POSIX.
If you have questions about Scheme 48, please feel free to contact us at s48-info at s48 dot org.