I'm guessing most people already know this, but I just discovered it, so maybe it will be new to some of you.
The toolbar's find box (Command-Option-F) will do non-contiguous searches. I discovered this when looking for a file called "bit depth and sample rate examples" and accidentally typed in "bit rate." It found the file even though the wording was wrong. I then tried "rate bit" and it found it again.
Pretty slick.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20040526163422234