I used Patons Shetland Chunky in a variegated blue and brown colour. The button was one I found in my scrapbooking stash. There is a crocheted loop in the top of the hat so it can be buttoned down for a different look.
I found the pattern through Ravelry. It's a free one and can be found here. It took less time than the length of a movie to knit.