This may be interesting for some of the newer fans to get a better feel for the history of the group.
The girls who are still active in AKB48 (or sister group) by generation:
First generation- Itano Tomomi
- Kojima Haruna
- Takahashi Minami
- Hirajima Natsumi
- Maeda Atsuko
- Minegishi Minami
- Sato Yukari (Team A --> SDN48)
- Urano Kazumi (Team A --> Team B --> SDN48)
Generation 1.5- Shinoda Mariko (failed the above audition, but got in thanks to the fans she acquired while working at the AKB48 cafe)
Second generation (Team K audition)
- Akimoto Sayaka
- Umeda Ayaka
- Oshima Yuko
-
Oku Manami- Kasai Tomomi
- Kobayashi Kana
- Sato Natsuki
- Masuda Yuka
- Matsubara Natsumi
- Miyazawa Sae
- Noro Karo (Team K --> SDN48)
- Ohori Megumi (Team K --> SDN48)
Third generation (Team B audition)
- Oota Aika
- Kashiwagi Yuki
- Katayama Haruka
- Tanabe Miku
- Nakagawa Haruka
- Nakaya Sayaka
- Yonezawa Rumi
- Watanabe Mayu
Fourth Generation- Kuramochi Asuka
- Ooya Shizuka
- Sato Amina
- Nakata Chisato
- Fujie Reina
- Nakanishi Yuka (AKB Kenkyuusei --> Team S)
- Deguchi Aki (AKB Kenkyuusei --> Team S)
Fifth generation- Ishida Haruka
- Uchida Mayumi
- Kitahara Rie
- Sashihara Rino
- Chikano Rina
- Nakatsuka Tomomi
- Nito Moeno
- Miyazaki Miho
- Haruka Kohara (Team B --> SDN48)
Sixth generation- Takajo Aki
- Nonaka Misato
Seventh generation- Iwasa Misaki
- Kikuchi Ayaka
- Komori Mika
- Sato Sumire
- Suzuki Mariya
- Maeda Ami
- Matsui Sakiko
And you can find the 8th, 9th, 10th and 11th girls in the girl index thread.
I hope this helps.