Public Domain Sound Archives?

Booker asks: "Are there any public domain repositories for sounds? Sort of like Propaganda for your speakers? Audio cues can really enhance a desktop design, but most of what is currently out there consists of a small number of bleeps, bloops, and buzzes. Of the window managers / desktops which do ship some default sounds (E, gnome, KDE...), where did those come from? If someone were to start such a repository, what should the file format be?"