Be careful!
I participated in a client conference call using an  access code the client provided. This was supposed to be a free call.  It wasn't. Although the client believed this call would be toll-free for participants, I received a bill with a charge for the call.

This is the number to "Free Conference Call.com" as they'll say when you call it.
You can signup on their website and get an access code to have a "free" conference call.  Toll rates do apply, though when dialing phone numbers to that area code.

It's a tele-conference number. You would need a Participant Access Code to join in.