Ever wondered what footage is sitting in your bin which you have not used? There's an easy way to find out and label them.
01) Hit Command + 4 to hightlight the Browser window. (if it's already highlighted then hit it again to bring it back :)
02) Highlight the sequence you're working on. (I type it's name once the Browser is the active window to highlight the sequence since it's faster)
03) Hit Command + F
04) In this find window (which is quasi-contextual so it'll look different depending on what's highlighted when you bring it up) set it to:
Projects: Set it to the project you're working on (up to you though, depending)
For: Unused Media (in selected sequences is up to you, again, depending)
Results: Ususally set this to Replace Find Results.
05) Hit the Final All button.
A list pops up with all the unused media that's in your Browser that has not yet been used in that Sequence.
What's cooler is that you can label them with colors right here.
01) Hit Command + A to highlight them all.
02) Hit Command + Option + any number from 1 through 6 to color label them.
Close the window and now all your unused clips will be color labeled in your Browser.
Be careful though. This is a broad way to find out what you haven't used. If you've used DV Start Stop Detection to make subclips or have made subclips of your own in a clip in the Browser and used one then that clip is considered "used" by FCP and won't show up in the search.