The ack command makes it easy to narrow the set of searched files to those of a specific programming language. For instance, if you have a rails project and only want to search the ruby files, use the --ruby flag with your ack command.

$ ack --ruby Active

With the --ruby flag, I get a manageable number of results. Without it, not so much.

$ ack --ruby Active | wc -l
      26
$ ack Active | wc -l
    5253

See man ack for more details.