Here is what I did last year: Plane Entertainment: Toddler Style
This year we don't have plans to go overseas but with baby #2 on the way we'll be spending a lot of time on the train going to/from doctor appointments, etc. My hope is to prepare some file folder activities. I need to get a laminaator first though...
A friend of mine posted a little while back about the file folder activities that she prepared for her 2 yr old. You can take a look at her blog post here.