Let's move from the popular to the less well known. One very popular option allows guests to sign a picture of the bride and groom. Simply take a picture of the bride and groom and have it matted in a mat several inches larger than the photo itself. Place a frame around this, but don't include the glass or Plexiglas frame. You'll add this later. Some people prefer to use "bulldog" clips to keep the mat together instead of putting the picture in the frame. The picture can be framed after the wedding.
Most couples choose a nice photo of themselves for this picture/guestbook option, although if there's a formal engagement photo, this is an excellent way to preserve that photo and show it off to friends and family. If photos are taken before the wedding with the bride and groom in their wedding attire, you can certainly use this photo. Many couples opt to either leave the mat empty or they place a temporary picture in the mat and add a wedding picture later.
Be sure to have a nice Sharpie marker handy and place the picture on either a sturdy easel or on a table where guests are sure to see it.
Another option is instead of providing a picture of the bride and groom to sign, the guests are provided with a picture of themselves! Simply provide a Polaroid camera and assign someone the job of taking pictures of the guests as they arrive at the reception. Once the picture is dry, provide a Sharpie and they can sign the picture, make a note to the bride and groom or hand draw a silly picture. It can be whatever the guest wants it to be. This is a unique, and personal, way for guests to 'sign in" at the wedding.
Whoever handles the taking of the pictures should also handle putting them in an album of some sort. A scrap booker might provide a special memory book with the Polaroid pictures in it, or the pictures can simply be placed in a nice album and presented later to the bride and groom.
Many guests don't give a great deal of thought to the guest book. They whiz by the guest book table more concerned with getting their cocktail and hitting the dance floor. If this is a concern, provide a 'traveling" guest book. Send each guest something either to sign or decorate before the wedding.
In this 'traveling" guest book scenario, there are several options. One of the easiest is to send each guest a small piece of paper and ask them to write something meaningful or thoughtful for the bride and groom on it. The pieces of paper are returned prior to the wedding (to ensure a better response, provide a self-addressed stamped envelope with the paper) and can be compiled in some meaningful way for the bride and groom and presented to them on their wedding day.
If the guest list is a creative or particularly close group, there is one other option that is even more meaningful. Again, in a scrapbook fashion, send each guest a piece of paper to sign or decorate. The paper should be the size of a photo album, so it might be a 6 x 6 piece of paper, an 8 x 8 piece of paper, or even 12 x 12, if the guests are up to that larger size.
In a letter that arrives with the paper, the guests are instructed to create a memory page for the bride and groom. They might include photos, quotes, little anecdotal stories, or combine all of these with stickers or embellishments. It's thoughtful, meaningful and personal and it's an excellent way to include guests who might not be able to attend the wedding, but would still like to be a part of it.