On DVDs, often the 'extras' include out takes or deleted scenes, sometimes even whole characters that didn't make it into the finished film (I'm working on a film at the moment where a character has disappeared completely between the first cut I saw and now, and there is another one who has been in and out of the film more often than I can count).
Books are the same. I have whole folders of deleted scenes. I have characters who have gone from being boys to girls or been written out of the story all together. In my first draft of An Unstill Life, Livvie and Jules had an older brother, and several of the things that ended up being Livvie's experiences were initially his.
I managed to recycle this character, with a few tweaks, for my next book, and often scenes I cut out are able to be used somewhere else, in another story. But I think there are still a lot of word graveyards lurking in the depths of my hard drives.
Do you re-use your outtakes or let them lie where they fall?