Here's a list in order of year:
Summer Storm (1944)
Summer Stock (1950)
Early Summer (1951)
Smiles of a Summer Night (1955)
Summertime (1955)
The Long, Hot Summer (1958)
A Summer Place (1959)
Suddenly, Last Summer (1959)
Violent Summer (1959)
Summer and Smoke (1961)
Summer Holiday (1963)
Summer Magic (1963)
10:30 P.M. Summer (1966)
Summer Fling (1966)
The Endless Summer (1966)
Japanese Summer: Double Suicide (1967)
Capricious Summer (1967)
Hot Summer (1968)
Summer Affair (1971)
Summer of '42, (1971)
Summertree (1971)
Summer Wishes, Winter Dreams (1973)
Summer City (1977)
Wes Craven's Summer of Fear (1978)
Corvette Summer (1978)
Pick-up Summer (1980)
A Summer in St. Tropez (1981)
Summer Lovers (1982)
One Deadly Summer (1983)
Summer Rental (1985)
One Crazy Summer (1986)
Summer (1986)
Summer Night (1987)
Summer School (1987)
White Water Summer (1987)
Aviya's Summer (1988)
Cold Summer of 1953 (1988)
Perfect Summer (1988)
A Summer's Tale (1989)
Summer's Lease (1989)
Warm Summer Rain (1989)
Summer Dreams: The Story of the Beach Boys (1990)
Bikini Summer (1991)
Summer of the Colt (1991)
Bikini Summer 2 (1992)
Indian Summer (1993)
Suddenly, Last Summer (1993)
My Summer Story (1994)
Last Summer in the Hamptons (1995)
Summer of Fear (1996)
Bikini Summer 3 (1997)
I Know What You Did Last Summer (1997)
I Still Know What You Did Last Summer (1998)
Summer of the Monkeys (1998)
Bullets Over Summer (1999)
Summer of Sam (1999)
A Storm in Summer (2000)
Summer Holidays (2000)
Summer Quenchers (2000)
Summer Catch (2001)
Wet Hot American Summer (2001)
...And Then Came Summer (2002)
Cold as Summer (2002)
Malibu Summer (2002)
Summer (2002)
Stolen Summer (2002)
Arizona Summer (2003)
Dead Summer/Deadhunter (2003)
Demon Summer (2003)
Summer Solstice (2003)
Summer with the Ghosts (2003)
Clara's Summer (2004)
Slutty Summer (2004)
Spring, Summer, Fall, Winter...and Spring (2004)
Summer Storm (2004)The Last Summer (2004)
How the Garcia Girls Spent Their Summer (2005)
My Summer of Love (2005)
Summer of Courage (2005)
Eternal Summer (2006)
Raw Summer (2006)
Summer '04 (2006)
Summercamp! (2006)
Summer Love (2006)
Summer Palace (2006)
Summer Rain (2006)
Summer School (2006)
Summer Scars (2007)
A Plumm Summer (2007)
Dog Days of Summer (2007)
Revolution Summer (2007)
Summer in Berlin (2007)
Summer 2007 (2008)
Summerhood (2008)
Summer Hours (2008)
Summer Lover (2008)
Summer Thunder (2008)
The Summer of the Massacre (2008)
500 Days of Summer (2009)
Costa Rican Summer (2009)
Last Day of Summer (2009)
One Hot Summer (2009)
Once Upon a Summer (2009)
Summer's Moon (2009)
Summer Wars (2009)
How I Ended This Summer (2010)
etc.
This can go on foreve