Nature sounds include ocean waves, rivers, whale calls, and pretty much anything else you can find in nature. A great distraction from outside noise while trying to sleep or relax.
Choose a track and hit to listen to the relaxing sounds.
Wikipedia - White noise Babies Online FREE Birth Announcements - Create a web site for your new baby, complete with pictures, instantly and for free! Tons of other great (and free!) stuff for new and expectant parents too, so check it out. About.com - Get information on sleep disorders and how you can treat them.