Well there are auto feed scanners out there, but they're really intended to auto feed paper documents, photos don't work well with them. Your best bet would be to get a decent flatbed scanner (I prefer the Epson Perfection line), put as many photos on the glass as you can at once and scan them in. Most decent photo software nowadays has the ability to automatically separate photos in scanned collages into separate files. Your other option is a professional company, most of them actually do fairly high resolution scans and are typically reasonably priced.