I buy cones of thread and wind them with a drill onto my empty spools to save money on thread.

I use some of mine to wrap binding on.

I cut the ends off (use a hobby/craft saw or have even used a kitchen bread knife-the one with the jagged blade)
then use the 'center' part of the plastic spool as an insert into the center hole of the larger spools. This 'insert' fills up the hole in the larger spool and centers it on the spool pin of the sewing machine. After the end pieces are cut off, if there are rough edges on the ends, these can be smoothed down using a fingernail file.

I've made angels with the serger cones too. They're perfect for a tree topper.

Many have said something about donating them to schools. As a former elementary school teacher and preschool director, those little bits of "junk" are gems. Preschool children use them as counters, additions to blocks for creating new structures (like the little boys and the forts) and for developing fine motor skills by stinging, stacking and learning how spools move. All in a days work for a child and an innovative teacher. At the very least as one message said, they make great additions to art projects for children of all ages.

If you have donated and wonder what the kiddos do with them, ask. Most teachers are happy to show off what their children can do. You may become a very special friend to that group children and can them how it happened that you got so many spools. Our quilts are another whole lesson in color, shapes, traditions and geometry for children.

At my Guild's bi-annual quilt shows there is a huge clear plastic jar filled with empty thread spools of all sizes, shapes and colors and whoever guesses the correct number of spools (or nearest number to it) wins a nice prize. I've been saving mine in a large empty pretzel container and will be handing them in soon as our show is in May. The DH of the gal in charge of the thread spool contest is the only one who counts the spools and knows the correct number. May in Jersey

my 4 yr old grandson stacks/tosses them in the back of his trucks to "haul" the logs. lol

I've been saving them for some reason, now I can offer them to my grandaughters school.

That is what I had in mind Ellageo. Something beautiful and neat. Thanks for the pic.

Doll furniture
 

Me and my sister use to make barbie furniture with them as we couldn't afford the real stuff... can make a table, and chairs...LOL bet kids don't think that way now