This is a new one I just came across today... Looks like a nice site.
I'm gonna have to do some browsing myself for my little guy.
It's basically a site where you can swap gently used clothes, books, toys, etc with others. When you sign up through the link, the first box is free, from there you post things you might have available to swap with others, the company takes care of the postage when you ship a box out. After you've claimed your first free box, additional boxes will cost you $5+ shipping. You can earn credit for shipping out boxes to others that you can then use to get more boxes for your child(ren).
Looks like fun.... But then, it's like shopping I guess :)