Really depends on the genre you like. I can fully focus and write when listening to classical and mellow instrumental hip-hop. I guess I should include other genres too.
Classical is kind of self explanatory.
Hip-Hop[Nujabes]
-First Collection
-Modal Soul
-Metaphorical Music
[Blue Sky Black Death]
-Late Night Cinema
[Fat Jon]
-Afterthought
-Humanoid Erotica
[Sage Francis]
-Personal Journals
[Cannibal Ox]
-The Cold Vein
Indie/Ambient/Avant-Garde[Andrew Bird]
-Andrew Bird And The Mysterious Production Of Eggs
-Noble Beast
[Belle & Sebastian]
Honestly, any of their albums.
[Helios]
As mentioned above, are really soothing.
[Colleen]
The Golden Morning Breaks (Highly recommended)
[Death Cab For Cutie]
All albums apply, especially Transatlanticism.
[Hauschka]
-Ferndorf
[Iron and Wine]
Majority of his albums.
[Kings Of Convenience]
-Quiet Is The New Loud
[Massive Attack]
-Mezzanine
[Mates Of State]
-Re-Arrange Us
[The Shins]
Get creative here...
[Quiet Village]
-Silent Movie
[Blind Pilot]
-Three Rounds And A Sound
[Brasstronaut]
-Old World Lies
[Camera Obscura]
I'd start with their older albums.
[City And Colour]
-Bring Me Your Love
-Sometimes
