I love this idea. An envelope guest book. You just take a store-bought scrapbook/album and glue envelopes into it. Lay out colored pieces of paper for guests to jot notes down on, and then they can place them in the envelopes.
Fun decorating idea for a baby shower or birthday party!- This would be cute for any party or shower. Just have to keep it high enough that kids wouldn't make a mess tearing them down if used for birthday.