Portable implementation of Simpler Macros and Modules
(Note this has become SRFI:72)
An experimental hygienic macro and module system for Scheme. Among other novel features, it eliminates a large class of possible capture problems that are often overlooked in existing hygienic procedural macro systems. In addition, it implements a convenient module system.
A manual, formal specification and portable implementation can be found here. A few simple examples are documented at simpler-macros-examples.