I actually have this information on the "RealCrappy" section of my blog, but I wanted to give it it's own post to make sure people are seeing it. This is about scanning in 12x12 or just large photos that do not fit on your scanner.
I just love this feature in Photoshop! Its called Photomerge, and is in CS3 and up. I understand it's availabe in Elements but I'm not sure which version. Here are the step by step directions. This is using CS6, but I've done it in CS4 and 5 with no trouble.
1. Scan each side of your 12x12. I actually scan it four times to get all four corners.
2. Open each scanned page and make sure they are all right side up.
3. Save each picture as something more unique. I usually give them the same name with a number.
4. In Photoshop, go to File, Automate, Photomerge.
5. Click on Browse
6. Upload the 2 (or 4) photos that you scanned and saved.
7. Choose collage.
8. Wait. Watch the magic.
9. Now it's all one photo! Click CTRL + E to merge them all together.
10. Use crop to crop it to the size you want and to get rid of any unwanted edges.
11. Save as a jpg. You may want to resize it--it will be pretty big.
And here's a video if you'd like to watch the magic happen!
Photomerge - Scanning 12x12 Photos Video
Wahoo! Love this new feature!