I was gonna suggest Rurouni Kenshin and Fruits Basket, but you've read both of those (FB was my first manga too) . . .
Nana is really good, as far as shoujos go. There is a lot of interesting character development.
Flowers of Evil if you can stomach incest and like tragedy. It's reallllly good, but sooooo sad.
Eden No Hana I love this story. Also has incest themes, but really, really touching.
Kuroshitsuji is a personal favorite of mine. Just very interesting and unique. (try reading reviews; the summary is not helpful at all)
Chiro Star Project soooo interesting! It's a really good shoujo, but mind you, the way the protagonist is treated is more than a little twisted.
Savage Garden has BL in it, though the main character is a girl . . . but anyway, it's also a really good manga (by the person who wrote Flowers of Evil). It's tone is dark, but the relationships and romances the characters have are interesting.
Dengeki Daisy is a pretty good shoujo, if you are looking for the Koukou Debut type thing, but it's nothing special . . .
Full Moon Wo Sagashite is really good, especially if you enjoyed Fruits Basket. It's sad, but the main character has multiple layers (she's always smiling, but you find out later that she's hiding a great amount of sadness inside her)
Shinshi Doumei Cross by the same author as Full Moon also reminds me of FB for some reason . . . maybe it's because the characters and their relationships are all really complex . . . but it's also good.
OH! HOW COULD I FORGET?
Vampire Knight is another one that you should at least try if you never have. It's one of those popular epic shoujos . . .
Anyway, it really depends on what you're in the mood for. I'd recommend all of these, but my personal favorites would be Kuroshitsuji, Flowers of Evil, Savage Garden, and Nana.
