Chronicle Books' new THE SOUNDS OF STAR WARS book contains a sound module for the 250 sound effects included with 300 photographs and behind the scene stories about the distinctive sound design for the STAR WARS universe.
From the Galleycat blog:
"Here's more from sound designer Ben Burtt, explaining how he created noises for the robot R2D2: 'I would close my editing room door and curl up in a quiet corner with the tape recorder and mic and generate baby talk ... I put myself into the mind of an infant and acted out a scene with a droid's intentions. I'd whistle and coo, I would sigh and groan, and at the same time I'd move the oscillators of the synthesizer.'"