Occupy Portland - Anonymous Communication
article on it: http://www.tgdaily.com/mobility-features/58830-how-to-occupywallstreet-anonymously-with-vibe
During the J20 counter-inaugural protests in 2004 in DC, I saw alot of people coordinating actions through a program called TXTmob. It was explicitly developed to coordinate actions and to evade police detection and might be something to look into.