A guy called Chris Karakas has made a very nice script to search through all files in a directory (and all subdirectories).
The original can be downloaded from http://www.karakas-online.de/downloads/grepdir and saved as /usr/local/bin/grepdir. If chmoded a+x then it can be used by all.
A note on ubuntu: I had to change the “/bin/sh” to “/bin/bash” in order to get it working (it was complaining about “/usr/local/bin/grepdir: 16: Syntax error: “(” unexpected”).
Update: A updated version that should read the shell automatically from the export list can be downloaded from http://www.f15ijp.com/wp-content/uploads/2010/08/grepdir