GNU GLOBAL is a source code tagging system that works the same way across
diverse environments, such as Emacs editor, Vi editor, Less viewer, Bash shell,
various web browsers, etc.

You can locate various objects, such as functions, macros, structs, classes, in
your source files and move there easily. It is useful for hacking a large
projects which contain many sub-directories, many #ifdef and many main()
functions. It is similar to ctags or etags, but is different from them in the
following two points:
- Independence of any editor
- Capability to treat definition and reference

WWW: http://www.gnu.org/software/global/