Prolific Programmer on the Internets!

Lifehack has a list of travel essentials. I do a lot of traveling myself, mostly internationally, and have a few additions to the list:

• The nearest consular office of your home country on paper.
• A list of prescription medicines you need, along with their ingredients, again on paper.
• A mobile phone that works in your destination country (this generally means an unlocked GSM phone).
• Change of clothes in your hand luggage.
• Foreign currency before departure. Yes, I know there are cashpoints everywhere, but who knows if they will honour your ATM network?
• Basic knowledge of the language spoken in the country you're visiting (please, thank you, "where is...?", "how much...?", "I don't speak ..." are most useful for most)