This tends to be the job of the IDE. I am working on a largish .NET codebase, and Visual Studio, combined with a plugin called Resharper is the thing that keeps

This tends to be the job of the IDE. I am working on a largish .NET codebase, and Visual Studio, combined with a plugin called Resharper is the thing that keeps that sane, giving us context menus that allow us to quickly find usages of a method, or implementations of an interface. For Java code, Eclipse performs similar functions.