For a while now, I've been using two voice over IP services to give my iBook, with its built-in microphone, something like an embedded phone. I've been using Skype for a while to call out so that, say, when I'm using wireless at the coffee shop and need to make a quick call, not having a cell phone is no problem. I plunked down $10 to make calls to phones, but now using Skype to make calls to phones is free. The quality isn't super, but it's much improved from even several months ago.

Three hints:
1.) Use headphones so that the sound doesn't interfere with the mike.
2.) Loud background noise at either end usually kills the reception.
3.) If you get a particularly bad connection, and you can usually tell during the initial rings, hang up and try again. I've never had to try more than twice to get a usuable connection.

Picture of Gizmo Dial interface. Finding a way for people to call me was more difficult, but I finally dug up The Gizmo Project's Area 775. This service surprisingly gives you a free phone number somewhere in Nevada that will make your computer ring. Messaging is also free, and will email you voice recordings when people call. It forces you to screen calls, and confusingly requires you to both hit an on-screen button to "accept call" *and* hit the "1" on the "dial," which only appears after you've discovered the tiniest icon at the bottom left that looks a little like the face of a phone.

Still, to be able to both call out and receive calls on your laptop -- or home PC -- for free is a nice thing to have. Free long distance means I can continue to hold off on the cell phone purchase. Okay, okay, well, in the interest of full disclosure, I did grab one of those pay-as-you-go phone for when I need the extra clarity or my laptop's not in a wireless network, but you still might surprise yourself at how well a laptop with a mike can mimic a phone. For free.