Here's a really cute idea. Frame quote bubbles, use a dry erase marker to write funny things your kids say. When you are ready to switch the quotes, have the child take a picture with their quote and make a photo book of quotes.
Love this Dry Erase Perpetual Calendar. Stitched and framed fabric, trimmed with grosgrain ribbon and framed. Dry erase markers used directly on glass -- they wipe completely clean. This calendar available via Etsy.