StillStream is an internet radio station that specializes in Ambient. They play all sorts of varieties of ambient, from hundreds of ambient artists. They have a very high quality assurance, too; I've rarely heard a bad song on StillStream. This is pretty weird, because they don't play any artists they can't get permission from (unlike most net radio stations), and yet they consistently play good stuff and rarely play songs twice (in a year, even). It's a great station to throw on when you want to relax.
StillStream website.
