Waltz #2 is CLASSIC.
The entire Death Cab library works quite well for me - anything off of We Have The Facts or Transatlanticism will have me bawling.
"Green Eyes" and "Amsterdam" by Coldplay
"The Longest Winter" by Pedro the Lion (and everything on that album)
then there's some stuff by U2
and Dashboard Confessional
and The Ataris
and...and...
And, well, as much as I was unimpressed with The Format's Interventions and Lullabies, their song "On Your Porch" is an amazing track.
...and I'm going to stop now. I could make an eternal list of wallowing. But I won't.