Free VoIP, make and receive IP Telephony calls. ineen has a laundry list of features which include voice, video, instant messaging, and most important - free. It is definitely a viable alternative to Skype and it has a nice interface. It is also available for Windows and Mac OS X. Try it out, its pretty nice!

For those interested in offering their own simliar product, ineen was built using Xten's eyeBeam SDK.