If you are interested in how services like Freeconferencecall.com make money be sure to check out this article in the Wall Street Journal (paid content). In short, large phone carriers like AT&T and Verizon have to pay 5.3 cents per minute to terminate calls in rural parts of Iowa due to the way the telecom regulations in the US work.
So free conference calling services, chat and sex lines were set up with numbers connecting to rural Iowa. The rural carriers split the incoming revenue with the internet companies.
The large phone companies started to block calls, the free conference calling services complained to the FCC and now the large phone companies stopped blocking calls and instead refuse to pay.
If nothing else this article shows just how inconsistent the telecom policies are in the US and moreover how technologies like the internet and IP communications have been able to open up large business opportunities.