Replying to Wasting idle time

So I am going to Europe this summer for about a month. I am back packing and going with a couple good friends. We'll be using the Eurail during the night as well as having a lot of layover time and idle time while we wait for trains in stations and such. We've got poker but I basically suck at it, so I am looking for something to take up idle time, I was thinking a nintendo DS or something, but I have no idea. I need suggestions.