Further to my RTFM presentation on "grep" at the April MUUG meeting, the following IT World article has a few interesting tips on using GNU grep:

http://www.itworld.com/it-managementstrategy/106032/how-to-grep-tricks-linux...

Note that the article refers to grep for Linux users, but the options described are applicable to the GNU implementation of grep, regardless of underlying OS.

GNU grep also has many other potentially useful options, so be sure to RTFM: grep(1).