I have one of these wooden spool holders. I used to keep my bobbins in a pillbox, but it was kind of annoying having to open each one to find the right color thread. (Labels kept falling off.) So it occurred to me the smartest thing to do is to keep the bobbins with their matching thread spools. Like this:
I still have more to do. I also need to buy some of those little hair scrunchies to hold the bobbin threads in place. But this will make it a lot easier to find what I need!