I know they make 12 x 12 scanners but last time I checked, it was out of my price range. I'm hoping someone can advise of a good one and that they have come down in price.
I gave up and purchased Adobe Photoshop elements 8. I scanned two halves of a 12 x 12 page and did photomerge panoramic. It worked great. The only thing I noticed was an occasional dark area in the middle where it merged together on light color pages. Usually a photo was in the middle so it wasn't noticable on all areas. Walmart.com had Photoshop for around $65.