Calling card or other cheapo phone calls to USA? (Sarajevo)

Context: I need to spend some hours a week on the phone to the states (and typically not in a setting where they can call back). Tried voice-over-IP phone but quality is iffy; and a 'real' phone but it's pricy for such heavy use...

So I was wondering if there are 'calling card' mechanisms or similar that people use to phone overseas? Back in the UK, shops were full of these things. You'd phone a local number, enter a pincode from a scratchcard, and then the target overseas number. Is anything like that available here?