There may be other attacks but I have just known that these two popular mobilizations in the USA have been brutally attacked.
Occupy Oakland saw its camp raided and flattened by riot police. Several people who refused to leave were arrested. Dan Siegel, a legal advisor to the mayor has resigned and called to “Support Occupy Oakland, Not the 1% and its Government Facilitators”.
Sources: Occupy Oakland, Washington Blog.
The brutality in Portland has been quite worse: Justin James Bridges (musician and sign language interpreter), who was not presenting any resistance, was beaten so brutally by the cops that his eyes went blank and has lost mobility in leg and arm, bing in critical care.
Sources: Occupy Portland, Washington Blog.
See also Occupy Together (with links to all kind of Occupy movements worldwide).