Stick'em to a bit of A4 before you scan them. I have a Fuji scansnap and it's very good, producing OCR'ed PDFs (hence you can search the whole archive for amounts or phrases with acrobat) very quickly - it also can scan both sides at the same time.

I think the current ones don't come with the OCR stuff included anymore, or with the full copy of acrobat either. ISTR mine was about 200+VAT. Does colour too, but it's not really up to photos, being something like 300dpi max.

Hugo