For multi-person chat, you could also check out reelportal.com
The quality is no where near big names like Skype, but when it comes to multiple party chats, all of them degrade significantly IMO.
I liked reelportal because its not a commercial service. Its written by one guy who just thought a flash-based app like this could and should exist for free. As such, the UI is kind of buggy and not all that pretty. But the functionality is just awesome- you can tell someone to sign in from any computer in the world with a webcam and flash installed (no software to install or account to sign up). Just type in a room name and an optional password, and go. Technically, they could do this from a library or internet cafe (do those still exist?).
Did a call recently between 4 people, including 2 desktops, a tablet and a phone, and was pretty amazed that it worked as well as it did for a free product. Also kind of cool to use as a security camera when I'm out- had one laptop in one room, a tablet in another, and could sign in from my phone and see what those two are seeing while I'm out. Pretty cool.
If you're willing to pay, though, skype is pretty much the standard by which all others are judged.
