This is old but good. Back, way back in college dorm life, at the end of the year they would charge us if there were holes in the wall or marks etc. My room mate would take out the spearmint green tooth paste and fill all the holes to clean up any holes. Worked great and we were never charged a cent.
If the hole is small enough, just rub the corner of a cake of white soap over the hole, and the soap will fill it just fine. I saw that technique years ago on "Queer Eye For The Straight Guy", and I've been using it ever since! (01/31/2010)
White toothpaste works for small holes. Just take a tiny amount and spread it with any straight edge at hand even a butter knife will do. Spread until blended with the white wall after drying for several hours. Can paint over this with any acrylic paint. (02/03/2010)