This sounds so much fun!
A: Ayumi Hamasaki, Ami Suzuki, Accross The Universe (musical)
B: The Beatles, Britney Spears, Buono!
C: C-ute
D: Daniel Beddingfield, Darin
E: Evanesence
F: ---
G: ---
H: HANGRY&ANGRY, Hello!Project (if that counts

)
I: Imogen Heap
J: JYONGRI, Jason Mraz
K: Koda Kumi, Katy Perry, Kelly Clarkson
L: Lady Gaga, Lily Allen
M: Morning Musume, Miki Fujimoto
N: ---
O: ---
P: Panic! At The Disco, Paramore, The Pipettes
Q: Queen
R: ---
S: Stephanie, The Sounds
T: Taylor Swift
U: ---
V: v-u-den
W: Wicked (musical), Wolfmother
X:---
Y: ---
Z:---
1,2,3: 30 Seconds To Mars
other: