I always like to listen to music that reflects how I'm feeling at the time so:

Manic:
Crystal Castles - "Baptism"
Battles - "Atlas"
Death Grips - "Hacker"
Robyn - "Call Your Girlfriend"

Depressed:
Andrew Jackson Jihad - "People II: The Reckoning"
The Antlers - "I Don't Want Love"
Bonnie 'Prince' Billie - "I See A Darkness"
Giles Corey - "Blackest Bile"
The National - "About Today"