Oh man, the list is definitely long and varied.  Oh, and be aware that I may know them by heart, but they'd be nowhere near in tune.  Lessee, in no particular order...

Happy Together - The Turtles

One - Three Dog Night

Old Fashioned Love Song - Three Dog Night

Lemon Tree - Peter Paul and Mary

Lumberjack song - Monty Python

Every Sperm is Sacred - Monty ( Read more... )