Starting May 21, Amazon Prime will be streaming The Sopranos, Six Feet Under, The Wire, Rome, Big Love, Deadwood, Eastbound & Down, Family Tree, Enlightened, Treme, Flight of the Conchords, plus some seasons of Boardwalk Empire and True Blood, HBO original movies, HBO comedy specials, miniseries including Band of Brothers and Angels in America, and several documentaries. Girls, The Newsroom, and Veep will eventually make their way to Amazon, too. (The announcement does not mention two of HBO's notable series: Sex and the City and Game of Thrones. Hm.)
I wonder if that's just in the US or international? I know that everything I want to watch isn't available on UK Netflix, maybe Amazon will be different.