Join ravelry.com (it's free, just register). You can search their pattern database (pictures) by limiting your search to garment, age, gender, type of yarn, and how hard the pattern is, as well as free or for sale patterns. I searched for "hat" with the parameters : crochet, child, free, easiness 0-3 (out of 10), worsted, and got 233 picture matches. Here are just a few of them:
http://www.leslieland.blogspot.com/
http://crocreations.blogspot.com/2011/01/tutorial-for-hat-with-bow.html
http://www.redheart.com/free-patterns/hat-and-scarf-boy
http://www.redheart.com/free-patterns/hat-and-scarf-boy
http://www.marloscrochetcorner.com/supersimplehat.html
http://www.bevscountrycottage.com/bev-hat-mitts.html