( From the website ) SLIB is a portable scheme library providing compatibility and utility functions for standard Scheme implementations.
SLIB supports Bigloo, Chez, ELK 2.1, Gambit, Guile, JScheme, MacScheme, MITScheme, PLT-Scheme (DrScheme and MzScheme), Pocket Scheme, RScheme, scheme->C, Scheme48, SCM, SCM Mac, SCSH, Stk, T3.1, umb-scheme, and VSCM. SISC is also a scheme system that supports SLIB but isn't found on the website.
If there are other schemes that can run slib please add them here.
The current version of slib is 3a3 (February 13, 2006). According to the website it is now a module system and a suite of tools to develop reflexive code.