I can only think of chill out albums since I'm not manic-depressive enough to get chilled and be done with it in 3 minutes.
Best chill out albums: Chill Out-The KLF (obviously), Disintegration-The Cure, Lifeforms-The Future Sound of London, Space.
Also, this free CD I got with a magazine once. I think its called The Blue Room. Radio 1 & Muzik, Mixed By Chris Coco & Rob Da Bank.