Brian Eno's "Apollo Atmospheres and Soundtracks" is superb and recently remastered.
9Beetstretch is a good one too. It is Beethoven's 9th symphony slowed down as to stretch over a twenty four hour period. It has been picth corrected so the notes are all correct. It is the sound of eternity and can be downloaded in chunks from here.
http://public.planetmirror.com/pub/9...retch/mp3/?fl=