I read somewhere that a mom keeps a postal box(About the size of a piece of paper and 2ish inches wide) and puts all of their art for a school year in that. At the end of the year, she seals the box and puts it in the top of her kids' closets.
I've also thought about saving some of my favorites and then taking pictures of everything else before trashing it. I have a fun project that I'm making with some of my kids' artwork and will share it with you in the next week or so.
What do you do with your kids' artwork?