Mostly I make all kinds of socks out of the sock yarn.
There is a good bit left over when a pair of socks is finished (using 100g sock yarn), so I might make socks that need 2 or 3 different colours.
I still have lots leftovers from the various socks I have knitted.
So there will be some monster socks, anything-goes-socks, that might only have the same colour in heel and toe.
And after this, the yarn that is leftover will have become less again, and it goes into a jar. This is pretty enough in itself and would work for me as a home decoration.
I'm making a sock yarn blanket out of the tiniest little bits. It's just knit stitches, and the yarn is held double. This is a long-term project, I've been doing it for about 3 years (though I haven't done anything for about 2.5 years, but I'm back motivated again to continue).
Sock yarn is great! I can justify buying lots because it will get used up eventually ;) I've been watching the World Cup in the last few weeks and needed something easy to knit without paying attention.
Check out my socks for sale and knitting patterns in my Etsy shop: https://www.etsy.com/shop/Gigi82Knits