Jill from Atlanta is really on the ball if this project is already done by February 15!
It wasn't until my house became littered with little Valentines that I remembered this trick. I had my kids gather up all the Valentine cards they'd received at school and make a collage with them on a piece of construction paper (front and back if needed). Now I have only one paper per child and it can "disappear" in a few days without me finding cards under sofa cushions for weeks.
Another idea: the very smart Valentine placemat!