It's like Enya on soma. Personally, I find certain types of Buddhist chant to be calming, especially ones with a group of priests that have a deep resonating bass presence. Couldn't really find anything decent on YouTube to represent it. I'll keep looking.
Edit: This is what I'm talking about, although the audio isn't the best. With a good set of speakers and a CD, this type of thing is amazingly calming.
Edit 2:Looks like the type of chanting I'm talking about may be unique to the Tibetan monks.