Ways to Connect to a Conference without using an Access Code or PIN

Direct call

US: +1 646 434 0515

Toll free USA number

Call +1 800 289 5570
When prompted; enter 9991426271 to connect to the conference.

Connecting from outside US

See details bellow on connecting using:

In-country access number - Call a number in your country to connect.
Skype - Connect with a free Skype call.
Webphone - free, web only, doesn't require download.

Different ways to connect result in different audio quality.
From any country you can use Skype or Webphone - these might give the best audio quality depending on the speed of your internet connection.

In country access number

Call your access number from the list.
Enter 883510001801948 using your phone keypad to connect to the conference.

Skype (free skype call)

Before the conference, find and add the Skype user with the ID : "confBridge" to your contact list. you can do it by clicking here or manually.

Make a regular Skype-to-Skype call to this user just as you would any other contact , regardless if confBridge is offline. Your call will forward your call to the conference provider free of charge.
When prompted, enter the PIN code on the Skype dial pad to join the conference call.

To switch to the Skype dial pad in Skype version 4.x, open it from the little arrow close to the volume control see image from the drop-down menu select Dial Pad.

To switch to the Skype dial pad in Skype version 3.x, click the "Call Phones" tab.

Webphone (Web only)

Register at http://webphone.nvcim.org/ and login.
At the input write: *011511@sipbroker.com (you can also copy & paste, don't forget the "*") and press Enter.

Credit due to: Noam Israel for facilitating all these ways.