I work in the PICU of a childrens hospital and I make hats for the youngest patients out of leftover sock yarn. Im starting to run out and thought I could ask here for donations if you dont mind. I can usually get 1-2 hats out of one ball of leftover sock yarn. PM me if you want to donate . The parents love getting homemade gifts and it adds a special touch to their stay. I can send you a pattern and photos of my hats too, if you want to knit your own.
Sock yarn is best because its thin for babies who require bedrest. Hats that are too bulky are not comfortable for them. Also make sure the yarn is soft and feels good when rubbed on the back of your neck or forehead. My fav sock yarn for hats is knitpicks felici yarn. Some of the pure wool is too rough.