I’ve made several hats, a scarf, and a couple of fingerless gloves using sock yarn. I also have an unfinished toddler pullover that uses self-striping sock yarn.
In addition to the above - shawls and cowls. You shouldn’t have to use another yarn for strength, if it’s sturdy enough for socks, it’ll be fine for anything else.
I’ve made hats, I’ve seen patterns for sweaters, I’ve made hackey sacks, (small balls filled with lentils that tween kids like to kick around in a circle.)
A light weather scarf, dog sweaters [my personal favorites in any yarn!], fingerless gloves, premie hats, shawls, a bag for your glasses, ipod or cell phone.
Camisoles, T shirts, Afghans (if you have the stamina). I’m continually looking for patterns using sock weight yarn. I find anything heavier to warm to wear regularly.
For the most part, “sock yarn” is just the commercial name for fingering weight yarn (about 7-8 stitches per inch) with some nylon added for extra strength. (Baby yarn also falls into this category.) It is generally knit on size 1-3 needles – smaller for socks, larger for other items.
Use it for anything that requires a fine yarn – lightweight tops, t-shirts, baby things, gloves, shawls, camisoles, scarves, etc., etc., etc.