oh there is Flow and ummm Utada Hikaru and Ayumi hamasaki, BeForU and Do as Infinity,Namie Amuro, Riyu Kosaka...... and many more but umm i forgot oh well i hope these help
Malice Mizer, Gackt, Boa,... um.. i forget the more.. but you could check out artists on www.animelyrics.com they have a section for j-pop/j-rock artists and though you wont be able to hear their songs.. you will be able to see some of the lyrics and get names.. mew hope it helps mew
My favs have already been mentioned in the previous comments. ^^
There's
Bands: L'arc En Ciel (surprised nobody mentioned this..), UVERworld, Babystars, Charcoal Filter, Road of Major, Savage Genius, Bump of Chicken, High and mighty color.
InariHime Says:
Try Asian Kung Fu Generation and Chieko Kawabe 8D
Kiraiku Says:
oh there is Flow and ummm Utada Hikaru and Ayumi hamasaki, BeForU and Do as Infinity,Namie Amuro, Riyu Kosaka...... and many more but umm i forgot
oh well i hope these help 
uzukitty18 Says:
Malice Mizer, Gackt, Boa,... um.. i forget the more.. but you could check out artists on www.animelyrics.com they have a section for j-pop/j-rock artists and though you wont be able to hear their songs.. you will be able to see some of the lyrics and get names.. mew
hope it helps mew
the ultimate miracle Says:
My favs have already been mentioned in the previous comments. ^^
), UVERworld, Babystars, Charcoal Filter, Road of Major, Savage Genius, Bump of Chicken, High and mighty color.
There's
Bands: L'arc En Ciel (surprised nobody mentioned this..
Artists: Chihiro Yonekura, T.M Revolution, Angela Aki, Aki Maeda, Rie Tanaka, Yui Horie, Hitomi Takahashi, Kajiura Yuki, Mika Nakashima, Misato Aki, Shimokawa Mikuni, Tokuyama Hidenori, Wada Koji.
And there's this current song i'm currently addicted to..might want to go check it out. ^^
Youtube--Aozora No Namida (tears of the blue sky) by Hitomi Takahashi
Syco Says:
X Japan. Oldies but goodies.
jou chin Says:
^0^! Sure~!
Alice Nine, Utada Hikaru, move, Ali Project, Home Made Kazoku, Chemistry, T.M. Revolution, Kazuki Katou, Suga Shikao, JAM Project, and many more.