A bit behind, aren't you?
Nightwish have been around for quite a while, and it was Tarja who really made them popular... I can't stand Tarja's voice.
Anette Olzon has more of a pop/rock type voice, which I can tolerate but she can sound bad, too. Their best vocalist (mostly because he's also rather unique sounding) is Marco Hietala - if you like his voice check out Tarot, a band that's been around since the 80s.
If you like the more pop sound that current Nightwish has you might want to check out Indica. Their last album was a little heavier, probably due to Holopainen influence. Despite the pop sound I find them rather catchy.
You'll probably like this song, too Pain - Follow Me
. A rather mainstream song for Peter Tagtgren, even compared to the rest of the album it's from.
Back to female vocalists, try After Forever, Stream of Passion, To-mera (for an interesting one). There's also Epica which a lot of people like.
If you have any questions about metal, ask. If I haven't memorized and am able to list several bands, their discographies, facts about them, who produced what albums/the studios they're out of, similar sounding bands, etc it will probably take me less than two minutes to find such info.