Vacation - the Go-Go's
Holiday Road - Lindsey Buckingham
Red Rubber Ball - the Cyrkle
Heatwave - Martha and the Vandellas
Summer in the City - the Lovin' Spoonful
Theme from A Summer Place (!) - Percy Faith
Silly Love Songs - Paul McCartney (did it come out in the summer?) I associate it with summer in a particular place.)
Wipe Out - the Safaris
Cruel Summer - Bananarama
Suddenly Last Summer - the Motels
School's Out(!) - Alice Cooper
Hot Fun in the Summertime - Sly and the Family Stone