Posted by Matt
I recently posted about a device that lets you make free phone calls, even free 3 way calls, but just the other day found a service that will let you set up free conference calls with up to 150 people! Check out: http://www.freeconference.com/ConferenceCall.aspx
I haven't set up an account with them, but was on a call with someone I know who hosted a call this way and it seemed very straightforward. When you set up a conference, the system sends an email to all of the people that you indicate you want to invite with instructions on how to access the conference.
The one drawback I found is that the call-in number is not necessarily toll-free, so callers (including you) may have to pay long-distance for the call. If they are using a company line or a cell phone with free long distance, that might not be a problem, but it is something to consider.
This could be a relatively inexpensive option for small businesses to try out phone conferencing. If anyone tries it out, please post a comment relating your experience with the service.