To be honest, summer Europe travel is very busy. You're probably better off looking at either spring or fall, unless you happen to see something wide open in both directions just before you go. That said, my experience (albeit relatively limited) with international standby travel is pretty similar to domestic. I just hang out a little closer to the gate in Europe, the one time flying out of HKG they cleared me at check in.

If you want a "training wheels" way of flying internationally, may I suggest Canada? There are some great cities to check out there. Depending on where you live, I'd suggest Vancouver, Toronto, Quebec City (if you speak French), Montreal (if you don't), or maybe even Edmonton if you want to check out the mall there.