The Gambit programming system is a full implementation of the Scheme 
language which conforms to the R4RS and IEEE Scheme standards. It 
consists of two main programs: gsi, the Gambit Scheme interpreter, and 
gsc, the Gambit Scheme compiler.

Gambit-C is a version of the Gambit programming system in which the 
compiler generates portable C code, making the whole Gambit-C system 
and the programs compiled with it easily portable to many computer 
architectures for which a C compiler is available. With appropriate 
declarations in the source code the executable programs generated by 
the compiler run roughly as fast as equivalent C programs. 

WWW: http://www.iro.umontreal.ca/~gambit/