Regarding the music: I found video game soundtracks to be especially perfect - after all, they're designed to be background music. But I think there's more to it than that. I've had years of conditioning such that when I hear the Warcraft II soundtrack I immediately get into a mindset of intense concentration and happiness.

Obviously it depends on your tastes and whether you have attachments to particular video games, but here are my favorites:

• Warcraft 2 Soundtrack: http://bit.ly/1081t8K
• Braid Soundtrack: http://bit.ly/11IFF6L (Fantastic music with a range of emotions.)
• Braid Music Mod by Schwab: http://bit.ly/10BNcN7 (Excellent fan-made music for the game Braid.)
• Might and Magic VI: Mandate of Heaven Soundtrack: http://bit.ly/W7CFan
• Heroes of Might and Magic IV: http://bit.ly/149y0vn
• Planescape Torment Soundtrack: http://bit.ly/10J2CQw

(non-video game music that go into the rotation)

• Any Ratatat playlist: http://bit.ly/10vLjW8
• Yo-Yo Ma Bach Cello Suites: http://bit.ly/IPl7h0 (Two hours of Yo Yo Ma cello.)
• Two Steps From Hell, Invincible: http://bit.ly/110Nehm (Epic.)