Quoted from JediPimp:
The only thing I don't like about using movie footage for voice and sfx sound bytes is that it's hard to find clear samples. They're usually mixed in with background sound effects and music and can sound messy.
You should try extracting the centre/dialogue channel audio from the movie/DVD/Blu-ray. That gives you some pretty good results. And you can enhance with some EQ and a bit of room reverb etc. Works great.
And YouTube Is a great resource for sound FX.