The Acoustic Ecology Institute has a great compendium of site links that feature environmental and experimental sound clips. One of my favorites is the “part guaranteed conceptual failure” Audio Recordings of Great Works of Art. (Perhaps it is considered a failure because it took me four mintues to get the RAM files to play.)

The sites that did have more playable clips had various licensing schemes but then what’s three notes between friends when you’re sampling. Even if those three notes lasts seven and a half minutes.

A true time waster if there ever was one.