DrewAdams has written library Lisp:help-mode+.el, which enhances the help that is built into Emacs (version 21 and later). It is an enhancement to standard library help-mode.el.

Links to Libraries in Help

Links to libraries are provided whenever library names appear in buffer ‘*Help*’. After loading help-mode+.el, library names in buffer *Help* have mouse-over links to the corresponding library code.

For example, ‘C-h v features’ describes the variable ‘features’; this description lists all of the libraries currently loaded in Emacs.

See Also: HelpPlus