As others have mentioned, I bring books (page-turner mysteries and crossword puzzles), magazines and newspapers to read. I also bring my checkbook, latest statement, and bills - then I go through and pay the bills, put on the stamps and mail them when I land. Not my favorite task, so I might as well get it done on the plane.

If it's a business trip, I get started on the expense report while on the return trip. Letter writing too - almost a lost art, but greatly appreciated by the recipient.