Some sad songs...
New Slang by the Shins (BEST!)
How Can I Tell You? by Cat Stevens
Wonderwall by Oasis
Comforting Sounds by Mew (warning: very sad, and very amazing!)
Everything I Do by Bryan Adams (I love Bryan Adams)
My Body Is A Cage by Arcade Fire
Happy songs...
Brighter Than Sunshine by Aqualung
We're Going to Be Friends by The White Stripes
Pictures of You by The Cure
Wild World by Cat Stevens
Here Comes the Sun by The Beatles