There are probably going to be a lot of companies doing what Jahjah is doing. But their website is pretty, so I like them.
What they do is let one make free calls in North America or to Europe and a few other places. Just visit the website, enter your telephone number, your friend's telephone number, and Jahjah calls each of you and then connects the calls. Sure, it's not as easy as pressing the keys on your phone's number pad, but (unlike Skype) you get to use your phone.
You don't have to sign up, but I think more calls are free if you and the person you are calling are registered. Also, there are some reasonable limits on how long you can talk per day/month. But this looks like a pretty good deal.
I wonder how long it will be before Google or Yahoo decides to buys them.