There have been groups that have sprung up overnight on Facebook and elsewhere about carpooling to #occupywallstreet. (search on FB for Carpool to #Occupy Wallstreet, the link is not showing up here).
If you are carpooling to NYC there are some things that you need to know.
Liberty Park (also known as Liberty Plaza and Zuccotti Park) is located in Lower Manhattan in the Financial District, right across from the World Trade Center. This is a very small congested area. Traffic can be horrendous and parking in the area is at an absolute premium. There is little, or no, on the street parking and what is available is probably metered. You might find some on the street parking in Battery Park City (across West Street, in back of the World Trade Center) and there are loads of parking garages. But the daily rates at these garages can be very expensive (2.50 for half an hour at the municipal garages and those are up by Chinatown. A bit of a walk to Wall Street from there).
If you decide not to drive into Manhattan, an option is to park your car on the street in one of the outer boroughs (Brooklyn, especially Downtown Brooklyn is closest) and take the subway (you'll need to buy a Metro-Card at the machines, it's $2.50 a ride). Just about every subway line in the city stops in the Lower Manhattan area. Check out http://www.mta.info for more info.
If you take the subway, any "oversized" handbags/backpacks are subject to search. Pack smartly.
Make sure to check the "no parking" signs. We have something called "alternate side of the street parking" where cars are not allowed to park on certain days and certain hours. If you're in this for the long haul, make note of those days and hours and be prepared to move your car.
Parking in Staten Island or New Jersey is another option. You could leave your car in Staten Island and take the (free!) ferry over. It's a short walk from the ferry to Wall Street and Liberty Park. There are also ferries that run from New Jersey, but do cost, and the Path train. http://www.panynj.gov/...
I noticed yesterday, while coming into work through the Brooklyn Battery Tunnel, that NYPD was stopping cars with out of state plates and motorcycles. If you do get stopped, pull some tourist talk, "going to see the Statue of Liberty, yada, yada". Do not say "I'm going to occupy Wall Street suckers!". Be smart and be safe and please be the change!