I was just over on the rabbit hole aka Ravelry looking for yarn suggestions for chemo caps. You'll be happy to know that KnitPicks made the cut! They had KP Comfy, Shine/Shine Sport, and the newest yarn, Brava on their list. They of course also mentioned 100% cotton yarns like the Simply Cotton. Basically anything machine washable and dryable that feels very, very, very soft. Absorbency is a plus! Softness is also key for knitting preemie caps. Stay tuned for more of Purlgirl's Adventures in Knitting for Charity with her Fellowship and Fiber group!