Hamsphere is a virtual Ham Radio Software that can run on Windows/Apple OS.
It simulates Ham Radio using VOIP like technology.
Hamsphere 3 can also run on an Android device.
Hamsphere 4 is very realistic and even approximates Propagation conditions.
You dont have to be a licensed Ham to operate but you can register with your call sign.
I have been using the system for 2 years now and really like it.
Have made many contacts around the world.
http://www.hamsphere.com