When I first started sewing I was naive, I just let my bobbins run wild in a shoe box. As you can imagine there was a LOT of frustration when it came time to fish them out, there is nothing quite like trying to untangle a mess of cotton to ruin a perfectly good sewing session. The more you fight the bobbins, the more they unwind, I feel like they just KNOW what they're doing and do it just to spite me.
Now, months back I was scavenging an op shop and found this beauty, its an old plastic powder jar. It still smells faintly of powder and is the perfect size to hold my bobbins. I quickly fished through my sewing shoebox trying to cut free every single knotted bobbin so they could all move in to their new home.
Super tip: a small piece of sticky tape on the tip of the thread and tape it to the bobbin case, this will stop them from unrolling.