Passport expiration date is OK?
Flights all booked
Hotel booked
Rental car booked
Get an international driver's permit
Arrange a ride to the airport (examples below):
Make a copy of all your credit card information and leave at home (or with someone here)
Copy your passport and carry it with you in your wallet
Inform your credit companies of where you will be
Lightweight your wallet (have a mugger's wallet)
Hold your mail
Arrange kid car seat situation (Rent with car or bring your own?)
Thermostat set where you want it while you're away?
What is your phone number where you will be staying (for all dates)?
Neighbors know how to get a hold of you?
Power adapters required? Do you have the right ones?
Airline rules on bag restrictions (Air Greenland for instance is lighter than US)