http://www.npr.org/2012/06/20/155132353/the-mix-the-songs-of-the-summer
I would add a few, stealing from Billboard http://www.billboard.com/charts/summer-songs#/features/summer-songs-19852009-1004102397.story, if you want to get more timely and are in heavy rotation:
#1: Fight Song - Rachel Platten
Photograph - Ed Sheeran (adore, adore, adore this song — his TV performances have been so on point this year)
Cheerleader - Omi
Honey I'm Good - Andy Grammer (aka the song that won't die)
Sugar - Maroon 5 (even though it was released earlier in the year, it just reminds me of summer; I hate their new one, "This Summer's Gonna Hurt Like a MF" simply because of the 'we had to use an expletive in our song title' factor)