At noon (their local time) on Saturday in most major U.S. cities, people will be gathering to show their support for the Wisconsin protesters. They encourage people to wear red and white, which is apparently a sports reference to a University of Wisconsin mascot.
You can use this webpage to find the street address of a gathering near you.
http://pol.moveon.org/event/events/index.html?tr=y&auid=7838803&action_id=238 I might be joining if the work pager doesn't go off. Not sure how "useful" the event is, but if the news coverage encourages the Wisconsin people to continue their own vigil, then I suppose it's time well spent.