There are so many to choose from...
Onitsuka Chihiro - Infection - Very powerful voice with extremely well composed songs.
Yonekura Chihiro - Forever Gate/Eternal Door - Very active fast paced songs.
Kotoko - Agony - Fast paced, good rhythm.
Kajiura Yuki - A Song of Storm and Fire - Probably the best current Japanese composer around. The vibrance found in her work easily eclipses that a lot of others even Kanno Yoko.
Two Mix - Love Revolution - Good group specializing in a lot of synthesized music that did a lot of Gundam music particularly Wing.
Chiba Saeko - Here We Stand In the Morning Dew - Great voice that can literally overpower the music (song composed by Kajiura Yuki).
So many great artists left unmentioned, yet so little time...
*Videos are, of course, irrelevant in several links.
