When scheduling a conference call in Microsoft Outlook or any other calendar program use this simple format for the number:
1-800-123-4567x1234567#
(PhoneNumer)x(Extension or Passcode)#
The Blackberry is programmed to dial the number before the "x" (the "x" stands for extension) and then prompts a dialog message with the numbers after the "x" to dial the extension. So when you hear the automated voice ask you to enter the passcode all you have to do is hit the extension button on the screen and it dials it for you. Pretty smart.
Here is s video of this feature in action on my Blackberry.
By the way, FreeConferencePro.com seems to be an excellent free service. I suggest you to try it out.
About the author: I am a veteran IT professional and writer. As an ECM Technical Lead for SunTrust Bank I spent the last 2 years implementing a new Enterprise Distributed Capture system. My first book, "Confessions of the Virtual Employee" (tentatively titled) is in progress and will help guild others on the benefits and virtues of being a modern Virtual Employee.