Depends on the holiday (leisure or adventure). I suggest some sort or reading app (Kindle, Nook, Google Books, Aldiko, etc.), a few games mostly of the mindless time wasting variety (i.e. angry birds, cut the rope, solitare or air control). I'd also make sure I had a good web browser if wifi is going to be available, a music/ video player that works with your music/video files that you wish to preload and possibly a mapping application that allows caching of maps so you don't have to have a data connection. Possibly a translator app, travel app and first aid app.
If you plan on using it to communicate, make sure you have your email account setup and something like skype or google voice for texting/calling. That's about all I can think of.