Offered for our mutual amusement...
"Hermione Hears The Bells" (really funny if you've seen Hairspray)
www.youtube.com/watch?v=RE4Xw1vRWwE
"Good Morning Voldemort!" (another Hairspray connection)
www.youtube.com/watch?v=WhcDb3Rc9Lk
"Jezebel" guest-starring Michelle Trachtenberg as Lavender Brown
www.youtube.com/watch?v=LD-rMNsQDkM
"The Man Who Shot Liberty Valance" Guess Who?
www.youtube.com/watch?v=iMKGqSsPR88
"Buttons" Quite simply the naughtiest HP music video I've ever seen. (WARNING: The ship explored is Hermione/Snape--but this is hilarious)
www.youtube.com/watch?v=vpL0ZLFX9VE
"No Good Deed" or "Wicked HP style"
www.youtube.com/watch?v=MovAMkWGWu4
Moulin Rouge a la the Hogwarts Girls
www.youtube.com/watch?v=hR8qjGLZG5A
Nature Boy - Harry Potter
www.youtube.com/watch?v=RAlLBkt21hc
The following ones could be considered spoilers for DH...
Spoiler
Severus & Lilly (this one is very sad--and brilliantly put together)
www.youtube.com/watch?v=3KB-pcVGSH8
The Prince's Tale
www.youtube.com/watch?v=xnFlO-audNE
Tears in Heaven
www.youtube.com/watch?v=CWmg1HdUWIM
My Immortal
www.youtube.com/watch?v=5yeTwKMW4DU
www.youtube.com/watch?v=3KB-pcVGSH8
The Prince's Tale
www.youtube.com/watch?v=xnFlO-audNE
Tears in Heaven
www.youtube.com/watch?v=CWmg1HdUWIM
My Immortal
www.youtube.com/watch?v=5yeTwKMW4DU