The newly released AT&T Call International for Android, BlackBerry, and iPhone might be an awesome VoIP app for making calls overseas. Note the word "might."
According to AT&T, the Call International app lets you use a Wi-Fi connection to place international phone calls from their supported AT&T phones, to anywhere and from anywhere in the world--for a fee, of course. Just sign up for a Call International account, download the app from the provided link, and make your calls. Your credit card will be billed on a monthly basis, and you'll be able to manage your account online.
While the rates do seem reasonable--calls to landlines in Canada, Mexico, and the U.K. cost 2 cents, 8 cents, and 4 cents, respectively--we're not so sure they're the lowest available. Interested parties might want to check out other VoIP apps like Fring, MagicJack, Skype, and Google Voice, all of which could offer some better options, depending on the country you're calling to, your country of origin, and whether you're calling a landline or wireless line.
Updated November 9, 2011, 5:56 p.m. PT: Added costs for calling landlines in Canada, Mexico, and the U.K.