My church is a collection center for this area. My women's circle did 14 (I think) boxes at our last meeting, and my Sunday school class is planning to take a Sunday morning to fill boxes.
I have two boxes--you can get the pre-cut kind that you fold together to make a box--to let each of my kids do one. I had planned on letting the kids do ones to match their genders/ages but I found some excellent deals on clothes today at JCP so I'm changing the boxes to one for a girl age 5 - 9 and one for a boy age 5 - 9. There weren't any clearance clothes for a boy Mark's age/size.
We always have a blast filling the boxes. I like to try and think of things other people haven't. Hobby Lobby has these little round colorful measuring tapes for 99 cents at the checkout, and I usually put those in the boxes. This year, I'm putting two t-shirts and a pair of shorts in one of the boxes because I got each item for $1.67. WM always has their $1(ish) stuff in their toy aisle this time of year--little packages of blocks and little loveys. Bath toys. I'd really like to find some sets of chalk and slates/chalkboards that would fit in the boxes.
I think it's a great idea for our kids to participate in the choosing, buying, and filling of the boxes.