If I had to live on an island with only four things they would be...
My husband would definitely have to be by my side. Not only for the obvious reasons (I couldn't live without him), but he's very intelligent so I wouldn't need a book to know what plants to eat, how to build shelter, etc. The benefits of marrying a military man!
Second, of course would be my Netbook, because it has wireless Internet and by the time I would have to live on an island, the Internet will be EVERYWHERE.
Third, a monkey so he could climb trees and get bananas, coconuts, and anything else eatable.
Fourth.... my son. Because he makes us laugh and completes the family. Although, he would get bored fast without video games!