Gonzui for Emacs is an Emacs interface of gonzui, a source code search engine. It is written in EmacsRuby. It uses LangHelp interface, so you can jump to a source code and bookmark a position.
Gonzui is available here.
http://gonzui.sourceforge.net/
Gonzui for Emacs is available here.
http://www.rubyist.net/~rubikitch/computer/gonzui-emacs/