Matty, a New Zealander that used to live in BA, keeps this list of blogs in English from Argentina: Bloggers in Argentina.
Couchsurfing: A great community of travelers and locals. The BA group is particularly active and there are always activities going on. A great way for tourists to meet up with people, and for newcomers to make friends.
BAExpats: The Buenos Aires Expatriates Group has lots and lots of useful information. The members are a wealth of info on so many different topics and it has been helpful for me in finding out things like price level, how to exchange money, how to get a phone plan etc.