ah- ha! for this first one, I try my hand at romance! (well.... sorta...)

JACK AND JILL (James and Lil)
James and Lil
Sat on a hill
a-gazing at the water
"I'd be a king
If you'd wear this ring
And change your name to Potter!"

So up they got
And back to Hogwarts did trot,
So fast it seemed like flying,
Where sure as fate, young Snape did wait,
And as usual was spying.

When Lil came in
How she did grin
To see Snape's discomfiture
Poor Snape it did vex,
And he tried to hex,
But James cursed him and took a picture!

PETER, PETER, PUMKIN EATER (Peter, Peter, Death Eater)
Peter, Peter, Death Eater
Was the Potters' Secret Keeper
But old Voldie he did tell,
And didn't keep it very well

POP! GOES THE WEASEL (BOUNCE! Goes the Ferret)
All around the Hogwarts Halls,
Mad-Eye Moody chased the Ferret
Moody thought it was all in fun,
BOUNCE! goes the Ferret.

SIMPLE SIMON (Simple Neville)
Simple Neville met a pebble
While walking on the road.
Said Simple Neville to the Pebble:
"Have you seen my toad?"

MARY, MARY, QUITE CONTRARY (Ginny, Ginny, What a Ninny)
---as performed by T. M. Riddle
Ginny, Ginny, what a ninny
Where did the chickens go?
Giant snakes and diaries make
Petrified students all in a row.

I HAD A LITTLE NUT TREE (I had a Whomping Willow)
---as performed by Remus J. Lupin
I had a Whomping Willow
Nothing would it bear
But some dismal howls,
And a ball of hair.
Then my three fri-ends
Came to visit me
And all for the sake of my Whomping Willow tree.