What do you do with your Halloween costumes after your kids outgrow them? Better question: where can you find Halloween costumes for this year that won't break the bank?

Two words: Costume swap.

According to Green Halloween, if half of the kids in the U.S. who celebrate Halloween swapped costumes, it would reduce annual landfill waste by 6,250 tons, equivalent to the weight of 2,500 midsized cars! 

Green Halloween is sponsoring National Costume Swap Day on Oct. 9, a day on which big and small swaps will be held across the country so kids and adults can trade in their gently used costumes from Halloweens past for a gently used costume that's new for this year. Saves money, saves the planet, and it's a great reason to get together with friends and neighbors. Win, win, win!

Check out the National Costume Swap Day site to find a swap event near you. Don't see one? Host an event of your own. Green Halloween has all the tips you need to make it an eco-tastic success.

And you can still get in on the fun even if swap events aren't really your scene. Try online swapping via thredUP's Halloween Costume Swap

Here's how it works: Just put together a box of kids' costumes and list it on thredUP.com. Be sure to flag it as a "specialty box." When someone picks your box, send it free of charge (they even schedule home pickup with USPS). Then you can browse other "Halloween Boxes" to find this year's costumes for your kids.

Not scary at all, right?

Also on MNN:

Easy DIY costume ideas

Homemade Halloween costumes

Green your Halloween with a costume swap
Trade in last year's costumes and pick up something "new" this year at a costume swap event near you.