Listening to Antarctica is a daily web diary, including audio clips (RealMedia) of ambient sounds and conversations onboard the Aurora Australis, a research vessel currently on its way to the Australian Antarctic bases. Margot Foster's next port of call is Casey Base.
SBaGen is software (Windows, Mac and Linux) that generates binaural beats - interactions between sound waves that mess with your brain, to induce sleep, relaxation, activity, and allegedly even hallucinogenic states. SBaGen relies on text-file presets (although it comes with dozens of files to experiment with) but if you want a "quick start", there's also the Windows-based Brain Wave Generator.
Ever wondered what the Aurora Borealis sounds like? The northern (or southern) lights generate VLF radio waves as well as light. These sounds have been captured here as hundreds of free mp3 downloads, and they make amazing ambient soundtracks. Random clicks, whirrs, pops and whistles, direct from outer space. The site also features other "weather sounds" generated by lightning storms and such, and explains how you can get your hands on a VLF receiver to hear the sounds yourself.