Assign each table a different anniversary year (i. table 1 would be anniversary year etc.) and let the guests at that table write notes to be opened on that particular anniversary year (a unique alternative to a wedding guest book).
Simple romantic wedding poem for the bride and groom - I Choose You by Ms Moem - This makes a great wedding reading for the ceremony, whether it is in church, or a less formal and non-religious ceremony.
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.