Regia has a reputation of producing excellent sock yarn.
Their Cotton Color Tutti Frutti II collection (with colorways named for fruits) is fun - whether you want to knit for an adult or a child. The yarn is wool free, and is made with high quality cotton and polyester fiber that is wound into the yarn for stretchability. It is made of 72% cotton, 18% nylon, and 10% polyester.
Each ball is 100 grams and 459 yards. One ball will make a pair of adult socks.
Machine wash, lay flat to dry. Made in Romania.