To see an updated members list, as of March 12, 2010, upon the effect of the shuffle announced at their 2009 Budokan concert, see http://filipinoakbfan.blogspot.com/2010/03/akb48-ske48-sdn48-members-list.html
As of November, 2009, this is how AKB48 (including SKE48, SDN48, and research students) looked like, one month before the announced team shuffle (announced at Budokan, August 2009) takes effect
Team A
Team K
Team B
Team S (of SKE 48)
Team KII (of SKE48)
SDN48
AKB48 Research Students
SKE48 Research Students
SDN48 Under
I believe AKB48 and SKE48 have different research students because of proximity; Akihabara is about 4 hours travel from Sakae (one-way), so it would be more practical to not have the same set of students for both teams / locations (considering not just the actual performance, but also the practices). Not sure why SDN48 uses the term "Under"; my best guess is it stands for Understudy, which, in Theater parlance, are people who fill in for the other performers in case those performers can't make it on a particular day.
Also, you'll notice that 4 members of SDN48 are also members of other teams; before the great 2009 Budokan shuffle, Yukari Sato is also a member of Team A, Kayo Noro and Megumi Ohori are also members of Team K, and Kazumi Urano is also a member of Team B, but once the Budokan shuffle takes effect (moved to December 2009 from the originally announced October 2009), they will be a part of SDN48 only.
So, who's your favorite?
