Another variation on this is using a 4x5 setup to do 9 images at a time, which fits nicely into a 36 exposure roll, and you don't need glass. The negs are not flat, but flat enough (I use an extra stop down on the lens for DOF). It isn't worth the extra trouble for all subject types, but is quite useful for some, like portraits. I tape the final 8x10's hinged back to back, so they read across like 3 rows of 6 images.
You can also scan a whole roll, but then you don't have contrast and exposure information.