http://www.f17strike.com/

Not the only thing being organized. There's obviously a difficult tension here between taking the time to organize stuff properly, and not waiting so long that Trump and his cronies have time to consolidate power.

While there seems to be some disagreement as to what happens on the 17th, it does seem to have been largely settled on as the first of multiple days of action. If nothing else, getting in contact with a group like this means you're in communication with the people who are trying to do something.