The Basics:

A Plan for what your family will do in a disaster is essential.
Choose a meeting place and discuss what you will do if phone service is disrupted.
Water: One gallon a day for each family member is recommended.
Food: Canned and ready to eat food for at least three days. Don't forget the can opener.
First aid kit
Flashlight with batteries. Lightsticks also can work.
Radio: solar powered, wind up, or battery powered. Don't forget fresh batteries.

Other Suggested Items:

Cash: In a disaster plastic bank cards often are useless
Prescriptions and medications
Diapers and baby food if you have a young child
Blankets
Protective clothing such as gloves, sturdy shoes and warm clothes
Clock with batteries
Matches, candles
Duct tape and tools such as pliers and a wrench
Camping stove, with fuel
Contact information for out-of-area friends
Map of your local area to identify evacuation sites etc.
Important papers such as health and vaccination records, insurance policy information
Medical essentials such as extra eyeglasses, hearing aid batteries
Personal hygiene items, bleach

To find out how to make a family plan and create a 72-hour emergency kit visit the Washington County Web site or the City of Beaverton. This site includes a labeled photo of a kit kept in a garage.
Similar information in a video slideshow format is available at The Oregon Trail Chapter of the American Red Cross Website. The presentation is comprehensive, but takes some time to view.
Another user-friendly site is the King CountyWeb site. The Be Prepared section covers everything. Check out the videos section for useful information on everything from natural gas and electricity safety measures to what would happen if Mt. Rainier erupted.