Occupy Wall Street seems to be the most "official" site connected to the demonstrations in New York City. Occupy Together is a related site attempting to help coordinate events in other cities across the country (and several outside the United States as well). The NYC General Assembly seems to be a (the?) major deliberative body behind the NY demonstrations and they have also issued a Declaration of the Occupation of New York which is the most explicit statement I've seen on the reasons behind the protests. For a history of the events leading up to the protests there is A Report from the Frontlines: The Long Road to #OccupyWallStreet and the Origins of the 99% Movement
Adbusters: Occupy Wall Street
Twitter: Occupy Wall Street
Truthout: Occupy Wall Street (Watch Live)
Reddit: Occupy Wall Street
The Guardian: Occupy Wall Street
Wikipedia: Occupy Wall Street