Specific Recommendations taken from my own sleep playlist:
Classical (anything you like)
- particularly Gregorian Chanting and the like
Electronic Music:
ATB (especially some of his newer stuff. Really soft Trance)
Chicane - "Salt Water" (it features Enya's sister Maire)
a lot of Moby's stuff
some of Robert Miles (particularly "Children (Dream Version)")
FC Kahuna - "Hayling"
Röyksopp - "Poor Leno"
Daniel Pemberton - "Spanish"
PPK - "Resurection"
Lost Tribe - "Gamemaster"
some of BT's music
Plumb (Plummet?) - "Damaged"
Andy Hunter - "Translucent"
Télépopmusik - "L'Incertitude D'Heisenberg"
Orbital - "Halcyon + On + On"
New Age/World Music:
Axiom of Choice - "Parvaz"
Ceredwen
Georgian Legend (several songs from the soundtrack)
Loituma (much of their stuff, at least)
"Kindle My Heart" (from the A Little Princess soundtrack)
Aeone - "Message in my Heart"
Alasdair Fraser (he has some soft Celtic music)
Altan - "Lass of Glenshee" (!!), as well as several of their other songs
AnĂşna - "The Flower of Maherally"
several songs from the A Beautiful Mind soundtrack
Braveheart soundtrack (by James Horner)
Cirque du Soleil has some soft and pretty stuff, particularly on the album Nouvelle Expérience
Clannad
David Arkenstone
David Blonski (!!)
Dead Can Dance (much of their music)
Deep Forest (their earlier stuff, mostly)
Delerium (much of their music - I have 2 albums)
E.S. Posthumus - "Nara"
Enigma (!! - particularly music from MCMXC ad)
Enya (!!)
Friedemann - "Sunshower"
Greg Ellis - "Form 3"
Gypsy Soul - "Epona's Wild Daughter" (!!) and "True Love"
John Whelan
some of Jon Schmidt
Keiko Matsui - "Deep Blue"
KĂla - "Sean Deora" (!!)
Sam Cardon's stuff (particularly the album Innovators)
Loreena McKennitt
Mychael & Jeff Danna - "The Child Deirdre"
Northern Lights - "Carolan's Ramble to Cashel"
Orison - "The Butterfly" (!!)
Scartaglen - "Chuagh Me 'Na Rosann"
Secret Garden
Sheila Chandra
Simon Wynberg - "Strathgarry"
The Spirit of Eden - "Legend of Cuan"
much of The Truman Show soundtrack
Celia Briar (The Dark Rose)
David Anthony Clark (!! - Terra Inhabitata)
David Downes (Pavilion - I think the album has a new name now)
Jon Mark (A Celtic Story)
Peter Blake (Private Dawn)
Peter Pritchard
Zamfir
Silk Road Journeys (Yo-Yo Ma & The Silk Road Ensemble)
Michael Conn - "Galician Journey"
Nomad - I have 3 songs by them which are excellent
Ian Ritchie - "Mbuti"
Mark Tayler - "Rodeo Costa Rica"
a few songs by Israel Kamakawiwo'ole
Vas - "Samaya"
Niamh Parson - "Fear of Bhata"
Cherish the Ladies - "A NeansaĂ MhĂle Grá"
Relativity (particularly "SiĂşn NĂ Dhuibhir")
Reeltime - "SĂle"
Joaquin Liévano
Bruce Mitchell
Aria - "Secret Tear"
Chorus of Tribes - "Lullaby"
Cusco
a few songs from the album "Pieces of Africa"
Geoffrey Oryema - "Makambo"
Hazma El Din - "Escalay"
Hilary Stagg
Jean Michele Jarre - "Oxygene"
Jeff Johnson - "Jasconius"
"Spanish Guitar Favorites" by John Williams
John Serrie - "Lovers in Motion"
Mark Isham
Mary Jane Lamond - "É Horò"
Michael Nyman - "The Promise"
Mike Oldfield - "Tubular Bells"
Mythos - "June"
some of Old Blind Dogs
Quinn - "The Crown of Life"
much of the Album Music for the Native Americans (Robbie Robertson & The Red Road Ensemble)
Sacred Spirits - "Yeha-Noha"
Ronan Hardiman (!!)
Solas - "The Maid on the Shore"
Vanessa Daou - "Near the Black Forest"
Will Millar
Dream Theater - "Wait for Sleep"
More Mainstream/Other Music:
bĂ´a - "Duvet (Acoustic Version)"
Idir - "Pourquoi cette pluie"
some Jean-Jacques Goldman
Lokua Kanza - "Le bonheur"
Leslie - "Le bon choix (Version acoustique)"
Donovan - "Jabberwocky"
some of the music from the Prince of Egypt soundtrack
Acoustic Alchemy
April Meservy - "Decide"
much of the orchestrated Final Fantasy music
some Inside Out songs
Jewel - "Hands"
Mandy Moore - "Only Hope"
Chris Thomas King - "Hard Time Killing Floor Blues"
One Handed
some of the City of Angels soundtrack
much of Sarah McLachlan's music
some Peter Gabriel
Some of these I only have one song by (I got them from compilation albums) and that's why only one is listed. For others, the artist may not have soporific music in general, but the song in question is very good in this regard.
Anything with "!!" I think is particularly good, though most of these songs are excellent for me. Some people don't sleep well with Electronic (Trance/Ambient/Triphop) music at all, for example.