Yahoo has announced that it plans to allow its IM users to make and receive calls from PSTN phones at rates that undercut both traditional phone companies and rival VOIP providers. Calls to the US are expected to cost about 1 US cent per minute (or about half of that charged by Skype and also almost half the price of that currently charged by Dialpad, a voip provider acquired earlier this year by Yahoo). We will need to wait and see if these rates are true per minute rates or whether they are based on a monthly subscription that includes a specified number of minutes.
If the new service is SIP compatible then Skype may find itself up against some stiff competition.
Mathew Ingram has more details.