Snow (short, for Scheme Now!) is something the Scheme programming language community has needed for a long time. Snow is a packaging specification and repository that has been ported across multiple Scheme implementations. Yow. Marc Feeley, long-time implementer of Gambit Scheme, is one of the primary forces.
Snow is a general framework for developing and distributing portable Scheme packages. Snow comes with a set of core packages that provide portable APIs for practical programming features such as networking, cryptography, data compression, file system access, etc. Snow packages can export procedures, macros and records.
While Snow depends on non-standard features of the host Scheme system, the APIs Snow provides can be used in most R4RS Scheme systems. The Snow framework is a specification of a package structure and a package distribution protocol. The framework is not biased toward an existing Scheme module system, but can be mapped fairly directly to many existing module systems allowing Snow packages to be used from code that is Scheme system specific as well as from other Snow packages.
Such specialized Snow framework implementations have already been written for some of the popular Scheme systems and efforts are underway to implement more. We have also written a generic Snow framework implementation that works on most Scheme systems but that does not achieve the same level of integration with the host Scheme system. It provides features which are helpful for testing portability of newly written packages and it is useful when a specialized implementation of Snow is not yet available for the host Scheme system. The generic Snow framework implementation currently supports a dozen host Scheme systems.