Facets is a large collection of core extension methods and module
additions for the Ruby programming language. The core extensions
are unique by virtue of thier atomicity. Methods are stored in their
own files, allowing for highly granular control of requirements.
The modules include a variety of useful classes, mixins and
microframeworks, from the Functor to a full-blown SI Units system.

WWW: http://Facets.RubyForge.org/