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I've recently been following Money Saving Mom. I love that her site doesn't just have coupons. She's got lots of freebies and other good deals and information. I'd recommend that you add her feed to your subs.
Yesterday she posted a link to ThredUp.

I'm wondering if any of you have ever used or heard of anyone using it for kids stuff. You all probably know that I am the queen of consignment. Our kids wear mostly used name-brand clothing. It looks like you go online, pick out a box of clothes, pay a really low price, then when you are ready, you post your own box. Looks like a really great deal.
Anyway, I wanted to be sure and pass this idea along. Let me know if you decide to use it and how it goes!