A tutorial I made for a dear friend, explaining how to scan a large artwork. It isn't the best possible way, but it works nicely for me, when needed.
Do forgive me if there's a mistake or few there and also for the size of the file. I hope all is clear enough and understandable. If not, feel free to ask additional questions
reminded me through comments that CS5 has a function for this. This is what she says:CS5 has a function that automatically does this for you. Go to: file-automate-photomerge. Then it asks for your scanned pieces (I don't use a frame, I just make sure I scanned every part, it does not matter if it has a big overlap, it needs overlap to work.) You don't even usually need to rotate them or anything, it will patch the whole thing back together if it is a good scan. Sometimes it does not work, but scanning again or cleaning up a bit can help it. I find it has a very high success rate.
So for those who have CS5, try that too. For me it doesn't work so well (it fails me when it comes to paintings), but that could be due my scans or due the type of painting. It works pretty amazing with lineworks, though!
Anyway, that's another option. Thank you, Ludjia, for a reminder!