In alphabetical (english) order, since the Budokan shuffle will confuse things. Listed are lastname first. These are only those whose nicknames I am aware of and those that have been used somewhere. Those not listed here means I don't know their nicknames, or have never seen them referred to anything other than their real names, or have already graduated (some graduates are in the list though). List only includes members of Teams A, K and B (for now).
The first list is nickname to real name (some have more than one nickname); the second (below) is from real name to nicknames.
LIST BY NICKNAMES
Aamin - Maeda, Ami
Acchan - Maeda, Atsuko
Akicha - Takajyo, Aki
Aminyan - Sato, Amina
Aminyan - Sato, Amina
Ayarin - Kikuchi, Ayaka
Chii - Nakata, Chisato
Chiichan - Nakata, ChisatoChii - Nakata, Chisato
Chikarina - Chikano, Rina
CinDy - Urano, Kazumi (pronounced Shindi by Japanese, the 4th letter is always uppercased)
Erepyon - Ono, Erena
Gussan - Noguchi, Reina
Haachan - Katayama, Haruka
Harugon - Nakagawa, Haruka
Harukyan - Ishida, Haruka
Kitarie - Kitahara, Rie
Kojiharu - Kojima, Haruna
Kojipa - Kojima, Haruna
Korisu - Oshima, Yuko (katakanized version of Cris? Actually Japanese for "little squirrel")
Krisu - Nakatsuka, Tomomi
Kyururun - Kohara, HarukaKrisu - Nakatsuka, Tomomi
Lovetan - Ota, Aika
Maachan - Oku, Manami
MaiMai - Oshima, Mai
Maririn - Shinoda, Mariko
Mariyannu - Suzuki, Mariya
Mayuchi - Uchida, MayumiMaririn - Shinoda, Mariko
Mariyannu - Suzuki, Mariya
Mayuyu - Watanabe, Mayu
Meetan - Ohori, Megumi
Micha - Nonaka, Misato
Miho - Urano, Kazumi (an old nickname she used in her early days in Team A, not to be confused with Miyazaki)
Micha - Nonaka, Misato
Miho - Urano, Kazumi (an old nickname she used in her early days in Team A, not to be confused with Miyazaki)
Mii - Minegishi, Minami
Miichan - Minegishi, MinamiMikachi - Saeki, Mika
Mikapon - Komori, Mika
Mikapon - Komori, Mika
Mikipomu - Saotome, Miki
Miporin - Urano, Kazumi (a name Mai Oshima uses for her)
Mocchi - Kuramochi, Asuka
Miporin - Urano, Kazumi (a name Mai Oshima uses for her)
Mocchi - Kuramochi, Asuka
Moechin - Nito, Moeno
Myao - Miyazaki, MihoNacchan - Hirajima, Natsumi
Nacchi - Sato, NatsukiNakayan - Nakaya, Sayaka
Naruppe - Inoue, Naru
Naruppe - Inoue, Naru
Nonti - Noro, Kayo
Nozofisu - Kawasaki, Nozomi
Nyan - Kojima, Haruna
NyanNyan - Kojima, Haruna
Nyan - Kojima, Haruna
NyanNyan - Kojima, Haruna
Nyaro - Kojima, Haruna (I think only Shinoda calls her Nyaro)
Okutama - Oku, ManamiPyon - Ono, Erena
Pyonpyon - Ono, Erena
Rabutan - Ota, Aika (Rabutan is the katakanized version of Lovetan)Reinyan - Fujie, Reina
Saechan - Miyazawa, Sae
Sakippe - Matsui, Sakiko
Sakippe - Matsui, Sakiko
Sasshi - Sashihara, Rino
Shiichan - Shizuka, Oya
Suuchan - Sumire, Sato
Shiichan - Shizuka, Oya
Suuchan - Sumire, Sato
Takamina - Takahashi, Minami
Tanamin - Tanabe, Miku
Tomochin - Itano, Tomomi
Tomo~mi - Kasai, Tomomi (not to be confused with Itano)
Tomomichan - Nakatsuka, Tomomi
Ucchi - Uchida, Mayumi
Ume - Umeda, Ayaka
Tomomichan - Nakatsuka, Tomomi
Ucchi - Uchida, Mayumi
Ume - Umeda, Ayaka
Umechan - Umeda, Ayaka
Wasamin - Iwasa, Misaki
Wasamin - Iwasa, Misaki
Yonechan - Yonezawa, Rumi
Yukarin - Sato, Yukari
Yukirin - Kashiwagi, Yuki
Yuttan - Masuda, Yuka
Yuttan - Masuda, Yuka
Chikano, Rina - Chikarina
Fujie, Reina - Reinyan
Hirajima, Natsumi - Nacchan
Inoue, Naru - Naruppe
Ishida, Haruka - Harukyan
Itano, Tomomi - Tomochin
Iwasa, Misaki - Wasamin
Kasai, Tomomi - Tomo~mi (not to be confused with Itano)
Kashiwagi, Yuki - Yukirin
Katayama, Haruka - Haachan
Kawasaki, Nozomi - Nozofisu
Kikuchi, Ayaka - Ayarin
Kitahara, Rie - Kitarie
Kohara, Haruka - Kyururun
Kojima, Haruna - Kojiharu, Kojipa Nyan, NyanNyan, Nyaro (I think only Shinoda calls her Nyaro)
Komori, Mika - Mikapon
Kuramochi, Asuka - Mocchi
Maeda, Ami - Aamin
Maeda, Atsuko - Acchan
Masuda, Yuka - Yuttan
Matsui, Sakiko - Sakippe
Minegishi, Minami - Miichan, Mii
Miyazaki, Miho - Myao
Miyazawa, Sae - Saechan
Nakagawa, Haruka - Harugon
Nakata, Chisato - Chii, Chiichan
Nakatsuka, Tomomi - Tomomichan, Krisu
Nakaya, Sayaka - Nakayan
Nito, Moeno - Moechin
Noguchi, Reina - Gussan
Nonaka, Misato - Micha
Noro, Kayo - Nonti
Ohori, Megumi - Meetan
Oku, Manami - Maachan, Okutama
Ono, Erena - Erepyon, Pyon, Pyonpyon
Oshima, Mai - MaiMai
Oshima, Yuko - Korisu (katakanized version of Cris? Actually Japanese for "little squirrel")
Ota, Aika - Lovetan, Rabutan (Rabutan is the katakanized version of Lovetan)
Saeki, Mika - Mikachi
Saotome, Miki - Mikipomu
Sashihara, Rino - Sasshi
Sato, Amina - Aminyan
Sato, Natsuki - Nacchi
Sato, Yukari - Yukarin (not to be confused with Yukirin)
Shinoda, Mariko - Maririn
Shizuka, Oya - Shiichan
Sumire, Sato - Suuchan
Suzuki, Mariya - Mariyannu
Takahashi, Minami - Takamina (wotagei: Minami, not to be confused with Minegishi)
Takajyo, Aki - Akicha
Tanabe, Miku - Tanamin
Uchida, Mayumi - Ucchi, Mayuchi
Umeda, Ayaka - Umechan, Ume
Urano, Kazumi - CinDy (pronounced Shindi by Japanese, the 4th letter is always uppercased), Miho (an old nickname she used in her early days in Team A), Miporin (a name Mai Oshima uses for her)
Watanabe, Mayu - Mayuyu
Yonezawa, Rumi - Yonechan
AKB48 members whom I don't know their nicknames, so will add them to the list above when I find out:
Akimoto, Sayaka
Kobayashi, Kana
Matsubara, Natsumi
Yokoyama, Yui
[Last Updated: January 5, 2011]