Go to the areas where the immigrants from that country/region congregate and look for deals there... They are ridiculously cheap now to most countries.
One is so cheap, that when I called my wife overseas (Taiwan), that I used a card with two minutes left on it and I talked for 20-30 minutes--they did not even bother to disconnect the call when the money ran out.
However, does anyone think that there are governments and others handing out these cards so they can listen in on long distance calls (was a plot device in some recent Tom Clancy type novel)? I do not give any important information (back accounts, addresses, full names, ID numbers, etc.) when using these cards or even calling overseas (even calling with "the phone company--like AT&T) has been fair game for espionage (industrial and otherwise).
-Bill