Every once in a while I see devices that transfers slides to your computer in catalogs like Sharper Image. As far as I know, they are full size when they are transferred. I know our local camera shop gets an arm and a leg to do it so I just break out the old Kodak carousel and screen.
My sister bought one of those "Sharper Image" scanners - totally frustrating to use. Painfully slow, too.
If you have a lot of slides to scan, one of the flatbed scanners with slide insert/holder is what you need. The HP models generally come with pretty good software for resizing the images and doing color touch-up work (though Kodachrome rarely needs much help in that regard).