Programmer Eric Wendelin says you can get a lot more done with sets of files at the command line once you've mastered the basics of
find, an old school search tool. Find in and of itself gives you the same functionality as Google Desktop or Spotlight, but because it's at the command line, you can pipe results into other tools like
sed and really get things done in a flash—like do a global search and replace. If all this is making you go "huh?" but you've dabbled at the command line before, hit up Eric's post, which is a nice intro to what you can do with
find. Here's another helpful introduction to the command line.