Sagittarius Scheme is a R6RS1/R7RS2 Scheme implementation with a lot of practical libraries, especially cryptographic libraries.
The Revised^6 Report on the Algorithmic Language Scheme
The Revised^7 Report on the Algorithmic Language Scheme
You can find the source archive and/or Windows binary from the main repository. The main repository contains instructions how to install from source archive.
For historical reasons, there are following two repositories.
At this moment, issues are tracked on Bitbucket as well as the downloadables.
Documentations are available via below links: