From the web page:

Larceny is a simple and efficient implementation of Scheme, based on a relatively simple optimizing compiler named Twobit. Larceny was originally created to serve as a test vehicle for research on garbage collection and compiler optimizations. Its development has been supported by NSF, Sun Microsystems, and Microsoft.

Varieties of Larceny:

Four different code generators serve as the basis for three different varieties of Larceny: