My friend in MATS 1 sent this out as a facebook post...i want to share it and save it....enjoy!!!
If your scanner is too small for your piece, and you have access to Photoshop CS4 or newer, scan it in pieces, then open them in PS. Go to File>Automate>Photomerge (in CS6, at least; can't remember if it's exactly the same place in the previous versions). In the dialog box, leave it set on Auto (upper left), and make sure Blend Images Together is checked (bottom of middle section), then click Browse (upper right) to choose the files to make up the whole. Click OK, then sit for a few seconds while Photoshop dies the work. I've only had it do something weird on me once; you might want to rotate the files to orient then the same direction before doing this. It's pretty cool!