I had about 2 balls leftover from mum's jumper. Now they have been sitting in the press (cupboard) for over a year and I'd been planning socks out of them. I'd found a pattern ages ago that helps you knit any yarn sock, all you had to do was know your gauge. I knit from the cuff down as I'm more comfortable with that way and now use kitchener stitch to graft the toes.
Now I can't remember where I got the any yarn pattern, But I think it was How to make any size socks with any wieght yarn by Nancy McMullen. Or you can try this one called a Sock-u-lator is available for free. Do you think one day I might remember I have a sock loom sitting in the box unused?
I also had enough to knit a bonnet which turned out slightly larger than I expected.