Of course, the official website is:
http://www.akb48.co.jp/english/index.html
Arsencoffee provides a huge service to the AKB fandom by providing english translations to member's blogs:
Stage48 provides a huge collection of translations of almost all their songs:
They have an english forum containing several useful tips if ever you plan on visiting the Akihabara theater to see the girls perform:
Saeyaka.com focuses on Sayaka and Sae, but provides a lot of AKB news
Wheresnatsuki focuses on Sato Natsuki, but I found the author's reviews on concerts interesting (but I don't always agree with them... no way I can match her reviews on their costumes though!)
More updated news, cool info and translations:
I visit more; I just don't remember them all now. Of course, you can drop by wikipedia, and youtube, and just search around yourself (do I have to do everything for you?). And all the other file sharing software (that you should be careful of also).
While I'm mentioning AKB fans, I should also mention Darkscorpion, who, along with a team, provides a lot of subs for the AKB fandom (can I join that team?).
Later...