To quickly defrost your freezer.
-  Remove the food and place in a cooler.
-  Turn off or unplug the freezer.
-  Place pans of hot water on each shelf; replace as they grow cool.
-  Place a floor fan in front of the open door. Turn on high setting. 
-  As the ice melts use a wet/dry vac to vacuum up the water. This way you don't get water all over the floor.
-  When the ice is all gone, dry  the shelves with a towel.
-  Spray with cooking oil spray and wipe off the excess. (This helps the new ice not to stick as much).
-  Turn the freezer back on for 15 minutes.
-  Load the food back into the freezer. 
Source: My mother and myself
By Nightsong from Hay Capitol of the World