I love the idea of nontraditional wedding guestbooks. There are so many fun ideas floating around the blogosphere I'm finding it impossible to choose. Can I please have more than one?
Let your guests type their love for you on a vintage typewriter. (Sadly, this beaut is sold.)
Find a fun graphic poster and have everyone sign it, like this one by twoforjoypaper.
Give your guests some props and a chalkboard (like this one), and you're sure to get some hilarious photos.
What's your favorite? Do you have any other fun ideas?