Postcodes in Iceland are three digits and go clockwise around the country, starting in the Capital Area. 

In a map of Iceland (pdf) you can see the location of postcodes. Postcodes of rural areas are within brackets. 

Postcodes Map of Iceland & the Capital Area.pdf (129 KB)

Post offices and cooperated postal outlets can be seen on a web map (flash). Rural postmen provide postal service in several postcodes. 

Postoffices and postal outlets - webmap