This all occurred because I got frustrated when I looked for a bobbin and found that the threads were all tangled. I know they sell Bobbin Buddies (12 for about $6.50) but we had some plastic tubing 3/8" diameter and I gave this a try. Cut the plastic tubing in about 1/4" circles, use your scissors to open up the tubing and VOILA - Homemade Bobbin Buddies.
You can see from the picture that the more thread there is on the bobbin the more open that piece of tubing is but it still encloses the bobbin thread. I think using 1/2" in diameter tubing would probably be the best. Twelve inches of this tubing costs about 25 cents. Lots of bang for the buck here.