I use them for dog toys. I layer 2-3 socks (selecting ones without holes) and stuff half of it firmly with batting scraps and a sprinkle of catnip then stitch it shut so the cuffs are left open & loose. They like to gnaw on the stuffed part and nose around in the sort of "flower" made by the cuffs. The cuff part also usually stays slobber free so there's a "safe" place to grab it to give it a toss. Great for indoor fetch games.
The catnip part probably seems weird but my dogs LOVE catnip. They don't get all wild like the cats do but they are always interested in the smell and will pay much more attention to a sock toy with catnip than one without.