I use
VoipDiscount for free international calls.
Roughly, it works as follows: You sign up, register your phone number with them and then either:
* dial a prefix number to route your call through VoipDiscount for free
* type in your number and the one you want to call on their website; they connect the call for a 5 cent set-up fee
* use their application on your computer, very much like Skype
One limitation is that you get 5 hours of free calls per week. If you call for longer, they charge you but it is something like 1 cent per minute, much cheaper than say Skype. Another thing is that you must top up I think €10 every half a year. It might seem odd to top up when calls are free - but they offer cheap calls to lots of destinations and some of them do cost money. I usually find that I use €10 credit every couple of months.
VoipDiscount is just one of many brand names offered by one company called Betamax.
This website gives you an overview of which brand name charges how much for calls to what country. Have a look at that and sign up with the one that offers free calls to the destinations you use most. In your case, you would want one that has free calls to Germany and Ireland, allowing you to call both ways free of charge.
It may take a couple of minutes to get your head around this all but in the end, I think it is worth it. I have been using VoipDiscount as my primary phone for four years now. Works like a charm.