These Halloween sugar cookies look great. Head over to Annie's Eats to see closeups of the cookies shown here. The recipes for the icing and the cookies are at the bottom of her post. She uses Royal Icing to decorate the cookie, something I've never used before.
The frosting calls for something called meringue powder. I found several sources for it online and many people say it is available from cake supply stores and craft stores like Michaels. Seems that originally the frosting was made with real egg whites, but folks are nervous about raw egg now-a-days.
[Image from Annie's Eat: http://annies-eats.com/2009/10/29/halloween-sugar-cookies/]