Updates are scrolling in chronological order to show progression since 8 pm, when police began arresting and beating protesters. (Multiple videos embedded.)
Update - 8 pm- reports from the LiveStream and Twitter (unconfirmed) indicate that arrests have been made, with possible pepper spray incidents and kettling. Follow the LiveStream (below) and PennyRed on Twitter for details.
Things are hazy at this stage, though from Twitter it appears that a group of protesters may have tried to march to Wall Street itself, and the police have responded with force. From @PennyRed's Tweets, as well as unconfirmed reports, protesters (perhaps around 1,000) in the financial district may have tried to move beyond the barrier to Wall Street. Again, this is still unconfirmed.
Protesters at the entrance to Wall Street are gathered in numbers, and a huge police force is present. The LiveStream is reporting an unknown number of arrests, and streamers are trying to get to where police are currently moving. In contrast to this, reports are coming in that NYPD escorted peacefully all those protesters who returned back to Zuccotti Park at the conclusion of the march.
Update - 8:30 pm - the LiveStream showed that the large group standing off with police at Wall Street democratically decided to return to Zuccotti Park. From that point, there may be another march to Bowling Green, with unknown numbers. It could be a very long night.
Update - 8:50 pm - Unconfirmed report that another NYT reporter was arrested tonight. Hard to believe this one until it's confirmed. Though if it actually turns out to be true, perhaps the NYPD is punishing the Times for its pathetic utter lack of coverage of tonight's events.
Update - 9:04 pm - Natasha Lennard, the NYT reporter who was arrested on the Brooklyn Bridge, has just Tweeted: "a new march is leaving from Zuccotti Park – serious."
So, the marching will continue, and this time, I'm assuming, without a permit. I don't think this is going to end well. Occupywallst.org has just posted a Re-Tweet from a protester that reads, "be careful everyone and protect your face."
This is getting tense. Police have surrounded the park where protesters are located, and the LiveStream is reporting that police are preparing for mass arrests if anyone marches though the park and leaves. I'll update if this becomes clearer.
Update 9:12 pm - PennyRed Tweets: "Woman being arrested and shoved in her car, asked what her name is, shouts: 'Troy Davis. Emmett Till. Martin Luther King.'"
Update 9:25 pm - Many on Twitter (as well as our own commenters) have mentioned that counter-terrorism units have been deployed. If true, and it appears to be the case, my dismay is profound.
Update 9:37 pm - Natasha Lennard (NYT) Tweeted about 20 minutes ago that mass arrests have happened on Broadway and Beaver. Few details.
Update 9:45 pm - Natasha Lennard (NYT) reports of baton beatings, is looking for confirmation. In addition, indications are that a large group still remains near Wall Street, with the situation unknown.
Update 9:55 pm - Keith Olbermann points out that a NY Daily News article just posted has the NYPD claiming that 200 protesters tried to break through the Wall Street barricades earlier, and were subsequently maced.
Update 9:59 pm - Seems there are breakaway marches leaving Zuccotti Park, where a large mass of protesters are gathered (as they are every night). There will be more confrontations/arrests. This I can guarantee with near certainty.
Update 10:02 pm - NYCLU and others Tweeting that police are barricading and arresting. LiveStream is following a breakaway march, and it is tense.
Update 10:10 pm - I don't like the Tweet I'm about to relay from NYCLU: #nypd is barricading zuccotti and threatening arrests, helicopters r hovering
And now, we have video evidence of police violence:
Thanks to Publius2008 for pointing to the video. There are many more that are coming out.
Update 10:18 pm - the LiveStream is releasing video from a police paddy wagon where some of the media team's members, who have been arrested, recount the brutality and show their injuries. This is insane. They broadcast live from the back of the police van.
Update 10:27 pm - Now, we have the video of the Occupy Wall Street media team broadcasting from the back of a police paddy wagon after being arrested! Must see: http://qik.com/....
We also have more video of police using batons, and many more are streaming in quickly.
Here's the embedded video from the local Fox station:
Occupy Wall Street Arrests; Fox 5 Crew and Protesters Hit by Mace, Batons: MyFoxNY.com
Update 10:43 pm - This picture was taken minutes ago:

Click on the pic to enlarge it.
Update 10:53 pm - According to The Lone Apple, who is listening to a police scanner on Android, police are tracking around 500 people marching to Pearl Street, and are awaiting them (potentially to arrest them). The picture in the update above may be from precisely that.
Update 11:05 pm - Multiple reports of police planning to move on the protesters, with some reports claiming that protesters are being kettled in the park with police vans as helicopters hover. Waiting for confirmation.
Update 11:08 pm - This Tweet from Keith Olbermann seconds ago: No offense meant but if you're a news operation and you're not covering #OccupyWallStreet tonight, you're not a news operation any more. Not sure why he added the "no offense."
Update 7:45 am - Hi everyone. I'm back after a long night, and while I haven't really had a chance to go through the comments, I do want to post these videos offered by his panic:
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Follow me on Twitter @David_EHG
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Background from earlier:
On-the-ground reports and video indicate that between 15,000-20,000 participated in today's #99Percent march that stretched for miles as Liberty Square activists met up with unions for a march on the financial district from Foley Square.
For the DK LiveBlog by joanneleon, please go here and Rec. it up.
From the LiveStream, which can be found here, the crowds are still large and quite diverse. (While the march officially ended around 7 pm, the LiveStream continues to follow the crowds.) Be patient with the stream as it switches from the many volunteer, mobile streamers following this march.
The police presence has been very heavy, with many carrying the infamous plastic handcuffs ringed around their belts. However, this protest march fulfilled all of its permit requirements, and there should hopefully be no arrests.
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5:15 pm - protesters were still gathering near Foley Square, in anticipation of what looks to be a march toward the financial district of over 10,000 (potentially).
5:24 pm - The march from Foley Square has just begun, and large crowds have already gathered in the financial district as police try to reinforce the barricades. The scenes are utterly inspiring. Since my coverage of the amazing protests in Israel, I've been waiting for this moment. Finally, it may be upon us.
5:48 pm - Crowds are still marching, making their way to the financial district. Amy Goodman from Democracy Now is on the scene amidst the massive crowds.
6:38 pm - Stunning. March still moving as financial district fills up. From the LiveBlog, Michael Moore Tweets that police have completely shut down Broadway, and some are estimating as many as 20,000. Additionally, it appears NBC and CBS led their nightly broadcasts with the march, which is still pumping. Clarknt67 is LiveTweeting.
Here is the release from Occupywallst.org. Just look at the organizational representation and recognized organizations the movement is supporting:
On October 05, 2011, at 3:00 in the afternoon the residents of Liberty Square will gather to join their union brothers and sisters in solidarity and march. At 4:30 in the afternoon the 99% will march in solidarity with #occupywallstreet from Foley Square to the Financial District, where their pensions have disappeared to, where their health has disappeared to. Together we will protest this great injustice. We stand in solidarity with the honest workers of:
AFL-CIO (AFSCME)
United NY
Strong Economy for All Coalition
Working Families Party
TWU Local 100
SEIU 1199
CWA 1109
RWDSU
Communications Workers of America
CWA Local 1180
United Auto Workers
United Federation of Teachers
Professional Staff Congress - CUNY
National Nurses United
Writers Guild East
And:
VOCAL-NY
Community Voices Heard
Alliance for Quality Education
New York Communities for Change
Coalition for the Homeless
Neighborhood Economic Development Advocacy Project (NEDAP)
The Job Party
NYC Coalition for Educational Justice
The Mirabal Sisters Cultural and Community Center
The New Deal for New York Campaign
National People's Action
ALIGN
Human Services Council
Labor-Religion Coalition of New York State
Citizen Action of NY
MoveOn.org
Common Cause NY
New Bottom Line
350.org
Tenants & Neighbors
Democracy for NYC
Resource Generation
Tenants PAC
Teachers Unite