How can I make a 3G video call (not Facetime) from an iPhone 4 to another brand's 3G phone? Is it possible by default? or any apps?
Edit 11 November:
I just found this today: No 3G video calling on iPhone 4
Yes, you can use Skype for that, if the app allows 3G video-chat. Skype is available for a lot of platforms. When you are at home, you can also use Skype on your computer so you don't have to use your (probably limited) 3G network.
If you mean standard 3G video calls (3G-324M) then no, the iPhone does not support these (and I doubt any (legal) 3rd party apps would be allowed that deep inside the phone).
If the other party does not have any other possibilities besides 3G video call, then I guess your only possibility would be to get yourself a phone that supports that.
I use Qik, made by Skype: http://itunes.apple.com/us/app/qik-video/id439715497?mt=8 Its product page says "Compatible with iPhones, iPod Touches that have a built-in cameras and iPad 2's with iOS4+. Place live video calls with other Qik users on iOS4+ devices or on Android 2.1- Android 2.3.3 phones (93% of all Android phones)."
I just got the Qik app and only have tested it once, but it worked fine over 3G on Verizon network.
Unfortunately Facetime is only available for Apple devices and a Mac running Snow Leopard.
You can try Skype?
This is free to users, by downloading the app and informing your friend of the apps function, you will be able to essentially have a Facetime call. Best of all, you will be able to use an existing Skype account which means if you already have one you will get all your contacts, credits, and data.