I used small wooden spools as knobs on the cabinets I store my fabric in. I wound turquoise and orange thread onto them to brighten them up, held down with a dab of Elmer's. I get lots of compliments on them.
I unwind bobbins that come with machines. I don't know what's going on under there and I don't want to try to use thread that is rusty or weak or in a million short lengths - life is too short to struggle with stuff like that when I have a whole shelf in my cabinet full of good thread! I do try to salvage the bobbins themselves, though, as long as they're not too trashed.