Free White-Noise Downloads
This site offers several versions of water sounds, vacuum sounds, and hair dryer sounds, so if your baby doesn't respond well to one, there are others you can try. They'll even help you burn the sounds onto an audio CD.
Three white noise soundtracks (of ocean waves and heartbeats) that can be looped for hours of calming sounds.
Free download of a running hair dryer, which mimics the "whoosh" sound your baby heard in the womb.