Most recient release I can think of: Dolphin Tale, should leave you smiling.
Then a few at random:
Let It Ride
Galaxy Quest
The Princess Bride
Jumanji or it's "sequel" Zathura, I keep flip flopping on which I like better.
The first 3 or 4 Pink Panther movies, the ones done while Peter Sellers was still alive.
Some you might not think of as cheer up movies but always make me feel better:
Grosse Pointe Blank
The Sting
Moonstruck, but that one works for me because the Italian family scenes remind me of Sunday mornings at my grandparents house when I was little...