Diomidis Spinellis's book Code Reading: The Open Source Perspective (Addison-Wesley) offers advice on how to approach large codebases, particularly those of open source software.
The Ruby Facets core library [22] is another collection of code that aims to provide utility methods for Ruby. This library covers some of the same ground as the Core Extensions, but also provides additional extensions.
If you need more complicated manipulations to the English language than the Inflector class allows, look to the Ruby Linguistics project. [23]