Most of the time when I am going to a long long vacation I just unplugged my refrigerator (making sure that it is empty first) while leaving only maybe 5-10 pieces of charcoal inside the refrigerator by putting them in a newspaper (make sure that the newspaper are open).
It is said that the charcoal eliminates odor effectively.
By searching it I realized that there many ways to eliminate the odor effectively.
Spread a layer of baking soda on a cookie sheet and place it in the
refrigerator overnight or until the refrigerator odors are gone.
Fresh Coffee Grounds:
Spread a layer of fresh coffee grounds over the bottom of a cookie
sheet and place in the refrigeratore overnight. A coffee smell will
linger, but will disappear quickly.
Activated charcoal is available at most pet stores. Spread a layer of
activated charcoal over the bottom of a cookie sheet. Place the cookie
sheet in the refrigerator for a few days, until the odors are gone.
Unscented Cat Litter:
Place a layer of unscented cat litter on the bottom layer of a cookie
sheet and place in the refrigerator for a few days, until the odors
Source - Housekeeping.about.com
wikiHow states that
Dissolve 1/2 cup of baking soda into a sink filled with warm water.
And use that to
Wash and rinse all of the parts before thoroughly drying them. Don't forget to wipe as much of the walls and floor of the fridge as you can, even under the crisper drawers.