Video courtesy of fringland
Phones available outside of the U.S. commonly have two cameras: One high resolution for taking digital phones and a front-facing lower-resolution camera for video calls. However, phones available in the U.S., rarely have this second camera. This is even true for devices like the Touch Pro2 which has a camera in its European model but not for its U.S. model.
The new HTC Evo, however, will be both available in the U.S. and have a front-facing camera. So, fring is providing video calling service in its updated Android app.
It can be used even with phones that do not have a front facing camera (like the Nexus One).