As a photographer -- one thing I look forward to is using the iPad to share my photos with others -- at church, on the sidelines of sports, at my kids' school. I use my iphone for that now, a larger screen would be better.
Nice large bible for reading and taking notes at church. I use my iphone for my bible now, but a bigger screen would be useful to also be able to take notes.
Couch/bed surfing of course.
Games -- though I'm sure my 3 daughters will play far more games on it than I will.
Magazines -- maybe ebooks. I'm not sure about books as I love reading books on my iphone because it is small and light and easy to hold for a long period of time.
Maybe load it up with tv shows or movies before going on vacation.
Car entertainment system for the kids (games, movies).