The only real problem with FaceTime is that you must be on Wi-Fi--not 3G--to use it. But you do have --with a little jailbreaking.

Tango

If you don't have an iOS device, or if you own an iOS device and you want to make video calls over 3G or 4G without having to jailbreak it, you can check out . A cross-platform mobile video-chat service, Tango works on both iOS devices and Android phones.

Tango is quick and easy to set up--all you need is your name and your contact list, and you can start calling right away. For you to call someone through Tango, the other person also needs to have the app installed. You can invite friends via text or email, straight from the Tango app.

Aside from the ability to video chat over a data connection, one particularly appealing feature of Tango is the ability to switch between video and audio during the call.