You can now make free calls to within the US and Canada from GMail. And make international calls at a low rate. If you have a Google Voice phone number you can also receive calls. Strong competition for Skype? More attachment to Google?
Update: It took a few days until this was up and running. Works well. I would also like a conference call mechanism attached. There may also be a problem if the number is blocked when calling free conference lines. Largely I still use my cell, but this is a convenient connection at times.