I may be in the minority, but I really like looking through those 'Skymall' catalogs they always have on SW planes. Do other planes have these? They have really unique items at ridiculously high prices, but they're fun to browse.
Crossword puzzles are my latest thing though. I bought a big book of *easy* crosswords at the $1 store and even though they're easier than the NY Times, they're still somewhat challenging without being depressingly so.
Also, portable CD players or walkmans are great especially if you buy or rent books on tape/disc. You can even check these out at the library. It's great for me because I get motion sick and have to glance out the window a lot to orient myself. It's hard to do this when reading, so being able to enjoy a book and look out the window too is a cool thing.