Since music by Chinese female vocalists is far and away what I listen to most these days, I can offer a few suggestions.
First is 梁静茹 (Fish Leong), whose music I've come to absolutely love (it's not surprising that I have a song by her in my sig)... I would recommend her "best of" album, 恋爱的力量 (The Power of Love Songs) without hesistation.
Who else? Faye Wong and Stef Sun I both listen to quite a bit of... 梁詠琪 (Gigi Leung) is still a favorite, though I haven't listened to her music all that much lately. 許茹芸 (Valen Hsu) has a voice that I absolutely adore, and 那英 (Natasha Na) is of course a staple of Chinese female singers, along with 林憶蓮 (Sandy Lam) and 梅艷芳 (Anita Mui, who passed away last year), though I don't care for those latter two's music all that much.
And then there are the bands, like Twins or S.H.E, though I still hold their popularity is mostly attributed to reasons other than their vocal ability. F.I.R.飞儿乐团 is a new group that's getting pretty popular, and features a female lead singer... I'm not crazy about most of their songs though (Fly Away is pretty good, though Fish has a song by the same name which I infinitely prefer...
)
~KS
EDIT: OK, apparently the MacOS X/Safari system I'm using on-campus doesn't have Chinese support installed... all the Chinese characters have been turned to question marks. I'll have to fix it later when I get home.
EDIT 2: There we go.