Methodwriter keeps excellent lists of popular songs of yester years in his blogs. If you haven't read them, please do.

They're often good choices that reflect the period those songs were first performed. This list is an addendum to his latest list: The Class of 2005 Playlist- We're Here, We're Alive, We're the Class of '05!

Anyways, here are my additions (mostly alternatives and punks). Most of them are from around 2005 but not all (ones in parenthesis are recommended songs that may fall out of the 2004-2006 range):

1. - The Killers (I love
   , but Methodwriter already covered it. Also try...
   ,
   ).
   
2. - Jimmy Eat World (also try...
   and cover of Wham!'s
   )
   
3. - Panic! at the Disco (also try...
   and
   ).
   
4. - Maroon 5 (also try...
   )
   
5. - Daniel Powter
   
6. - Coldplay (also try...
   and
   )
   
7. - Keane (also try...
   )
   
8. - Arctic Monkey (also try...
   )
   
9. Marching Bands of Manhattan - Death Cab for Cutie (also try... Brothers on a Hotel Bed and
   )
   
10. - James Blunt (also try - Goodbye My Lover,
    )
    

EDIT: Extra bonus. How could I leave out Green Day?