Bakuman is good. By the Authors of Death Note. Different style but you can feel there's something familiar.

NANA manga. Progressively good, but not now...

Anything by Ai Yazawa (Gokinjo Monogatari, Paradise Kiss, NANA, Kagen no Tsuki) is recommended to the girls.

Gakuen Alice. Amazing shoujo. Target audience was Primary students but you don't see the issues they can relate to....

Kekaishi. Manga about 2 rivals family in the arts of Kekkaishi.

Bleach. Please. You heard about it all year long........

X. One of the most classic CLAMP come up with.

Sailor Moon. There's differences with the anime and the Manga, and the Manga is much more twisted and realistic... And pretty.. 8O