One excellent resource is The Daily Knitter, and also their free pattern finder. Via an email inspiration from them, I did a search and found the following free holiday hats:

Free Striped Elf’s Hat:

Family Elf Hats:

Snowman Hat:

Fling + Cotton Chenille Splash Holiday Hats:

And, the most adorable thing I’ve seen all day … The Rudolph Hat!