http://www.mhtest.com/ has done it before, maybe you won't even have to send them your
boards :)
For many purposes I think I'd be happy with a good 600 DPI color scan of both sides
(including silkscreen). I don't think that modern PCB processes will by default
produce a board that "looks like" an Altair era board (I remember the silkscreen
actually covering tinned solder pads.)