From the book Compiling Lambda Calculus.
Provided under the Creative Commons Zero (CC0) licence.
The ZIP file contains the complete source code from the book. Some of the more interesting parts can be viewed below.
Scheme0 compiler and interpreter, classic model
Scheme0 compiler and interpreter, environment propagation
Scheme3 compiler and interpreter
Scheme3->C compiler and runtime support
LC-language->C compiler and runtime
Lambda Calculus reducer