Pantyhose! Works great, makes a stretchy little sleeve. I also use this on my embroidery thread in my embroidery machine. One pair of old cheap panty hose makes alot of thread holders.

I like to use elastics for the spools of thread because I found that tape left a sticky residue, and I hadn't thought of some of the members of this board's resourceful suggestions.
For bobbins, no matter how well I wound the thread around, my bobbin case always had a mess of threads all over everytime I opened it. I tried the mini pony tail holders, which held the threads tight on the bobbins; however, they obscured the colour of the thread that was on it.
Then I read a tip that works really well. Go to your local hardware/home supply place/aquarium shop and get some clear tubing. Use a sharpie or a similar pen and make a little mark on the tube that is a bit smaller than the inside width of your bobbin. Then, on the opposite side that you made your marks, cut straight down the clear tube so that it can open up. Once you do that, you can just cut across the tube where the marks are. You end up with a bunch of rings with a slit on one side that you can open up like the letter "C" and slip over your bobbin. Hope that makes sense-- it would be a lot easier if I could just draw a picture. Most of us quilters are pretty visual people!

Thank you all so much, don't know which I will try, but at least I've got some new ideas.

If my thread spool doesn't have a slot, I make one with something sharp pressed into the side of an end. It's the bobbins that drive me nuts and I love the aquarium tubing fix. I bought a tackle box and keep spool and bobbin together in sections because I was having trouble matching the exact shade of ecru, ivory and white or grey, greyer or greyish threads off the spool with the started bobbins. Now if they're in a little section together, they belong together. I can also change the section sizes and if I have multiple spools the same colour they stay together with a bobbin.

I use scotch tape, especially if I know I won't be using it any time soon.

I had the same idea, but I buy the fuzzy ponytail holders (for children) at the dollar store. They are easier to remove with my fumble fingers. :oops:

Blue Painters tape works the best and doesnt leave any sticky residue.

I just wrap a rubberband around the spool.

Thanks for the tips everyone! :D

If my spool doesn't have a locking mechanism, I use this medical tape. I cut about 2-3" strips and cut those into even thinner strips (after all - I'm only trying to trap one thread. I'll attach a picture. It works great. It sticks only to itself - not my thread. I use the same technique on the bobbin thread and make it about as thin as I can get it, so I can still see the color on the bobbin.

I like this stuff so much, I wish they sold it in black so I could harness my extension cords with it. I think I will try it on my toaster oven, crock pot and blender cords while they're stored in the pantry though. Humidifier? Razor charger... Cords Under computer... Hmmm