Free library at your fingertips
Every time I take a long trip I try to bring a book along to read on the airplane just to pass the time. With the advent of e-readers like the Kindle, you can bring a huge library of books with you with just a few ounces added to your carry-on bag. One resource that I have found to be amazing is the library at Project Gutenberg. You can download books that are now in the public domain and read them in various electronic formats. The price cannot be beaten (free) and the amount of books available increase every day. They provide the books in file formats that work on the iPad, Kindle, Nook, OLPC and various other reader units as well as regular computers.
As a plus, these books are in the format the author originally published them, not edited or censored.