Pacific Northwest Railroad Archive uses Epson scanners, primarily the V800 and V850.  I particularly like that the the associated computer software lets you tweak the scan parameters based on your preview, before you do the final scan.  So minimal photoshopping afterwards!  I have only done prints on it, not slides or negatives, but I know it has the capability.  I believe the V850 slide template will hold 12 slides at once.  It's not cheap, but it is a very good scanner.

Chuck Soule