I used to prefer harder wools, because they are elastic, don't split and don't pill — they're easier to work with. But they are also itchy. Besides, it's only cold enough for wool for a few weeks where we live. I've started really liking cotton and linen yarns.
I've found two cottons that I really like. One is blue sky cotton which is fluffy and thick and the other is Rowan pima cotton, which is smooth and comes in a beautiful palette. This hat is pima cotton in millet. I used one and a half skeins.
Cotton is light — it's nice nice to knit with in the summer, when I have the most free time to knit. I did most of this hat last year on summer vacation. The pattern is for babies: it's the pom-pom cap by Hadley Fierlinger. I thought I had lost the chance to make it in time last year, but I thought I may as well finish it it and maybe give it to another baby. However, I had a nice surprise — it fits my three and a half year old well. I was going to do a big fluffy yellow and orange pom pom that he was excited about. But in the end, he likes it plain and we didn't need the ties either. It keeps his ears warm, but it's very light and not too warm for running around in.