Looperman.com you need to sign in to it to download any of the samples but it's free. They mostly have music samples but I remember seeing actual sound effects while I was on there the last few times.
freesound.org was my first thought, but he's wanted to steer away from the really well known ones for some reason. Trying to find undiscovered ones, I guess.
I'll pass it along regardless.. any more?
My local library had the entire BBC sound fx library. They aren't new and are well known but it's a huge high quality library. I would check your local/college libraries. You never know, you might find BBC, Sound Ideas or some other major library.