"Operation Payback" has had its website shut down. It's currently only active through Twitter: http://twitter.com/Anon_Operation. Twitter is also hosting Wikileaks: http://twitter.com/wikileaks. I am confident that Twitter will also cave in shortly.
Facebook is also still up: http://www.facebook.com/wikileaks.
Wikileaks recommends using reddit to spread information: http://en.reddit.com/domain/wikileaks.org.