Where can a developer find free, high-quality audio samples for use in an application?
I'm specifically interested in sounds like you might expect when you have a new mail message, when a scheduled appointment is happening soon, or when your electronic device is fully charged. Things like a nice metallic beep with a smooth echo, or a soft two-tone harmony.
Along the same lines, are there any good free (or cheap) apps that a developer could use to make those types of sounds?
This is the audio equivalent to, "where can I find awesome free icons?"