Here are some that popped into my head today:

Puff, the Magic Dragon - - Onward Christian Soldiers
Beethoven's 9th "Ode To Joy" - - various nursery rhymes, e.g., Twinkle Twinkle, Little Star, Mary Had A Little Lamb
How Can I Keep From Singing? - - Barbara Allen

And, via Garrison Keillor from his camp days as a youth, Praise God From Whom All Blessings Flow - - Hernando's Hideaway

Blue Hawaii - - Wayfaring Stranger