If you sign up with Thred Up (used children's clothing), you will receive a $10 credit. The credit can even cover shipping, which is rare! Unfortunately, shipping is $6.95, but you can still pick up a free or cheap article of clothing. (Sort by price, if you want to.) The sizes were even high enough to fit my size 14 son.
If you want to spend more, they have free shipping on orders of $30 or more.
You can also look into selling your used children's items through them.
Thank you for using my referral link. If you make a purchase, I get a $10 credit. BUT . . . if you share this deal with someone, don't give them mine, give them your own! They get $10 and so do you — possible freebies on both ends!
(Thanks, Chasing Bargains!)