More and more of these little free calling sites are popping up. Most are flooded with traffic before I get there, but this one, FreeRinger, seems to be holding up pretty well. The only catch is that your friend needs to call-back to a FreeRinger number, but you get 10 seconds to explain the situation to them 
Anyhow, try it out yourself right here. And no, it won’t dial 1-900 numbers you pervert! 