I've been in choir for over 15 years, and well, I absolutely adore musicals....
The ones I've seen live
The Lion King
Joesph and The Technicolor Dreamcoat
Les Mis
The Man of La Mancha (Don Quixote)
Beauty and the Beast
Bye Bye Birdie
High School Musical (yeah I saw it live... wasn't that great)
Ones I've seen recordings or movies of
Phantom of the Opera
O Brother Where Art Thou
The King and I
Singing in the Rain
The Music Man
Sound of Music
(i know there's others i've seen but I'm having difficulty remembering at the moment)
My favorite would have to be Man of La Mancha or The Lion King on Broadway, the soundtrack, if you havent heard it you should definitely check it out... its amazing, the costuming was even more amazing and the acrobatics involved in some of the scenes are just breath taking.