Say what you will about printers, I've found my HP machine highly useful. The scanner has an automatic size detection that works perfectly, and at 600dpi with tons of format options from PDF to JPEG to 1-bit black and white TIFF (I guess for faxing purposes?) it's never disappointed.
Though experience of trying to run it over the network is predictably abysmal, but since you have to bring your documents to the printer anyways to scan them, I have a USB drive set aside for scanning directly onto. Saves a lot of time and trouble.