Many families put out cookies and milk out for Santa Claus on Christmas Eve. WebMD offers some healthier ideas for Santa Claus. Some families are now also putting out Magic Reindeer Food which is a mixture of oatmeal, sugar and red or green sugar crystals. The food is sprinkled on the front lawn to guide a path for Santa's reindeer. You can see recipes here, here and here. Magic Reindeer Food can also be purchased - Miles Kimball sells it here.
Leaving milk out is likely to attract some curious pets as explained by the funny LOLcats graphic below.