I have a friend who makes his living selling vintage cereal boxes, which is a fine and honorable profession. But come on, there's no geeky vintage collectible cooler than the box art from plastic model kits of the 1955-1975 era (I'm in real danger of hitting eBay for an unassembled Revell Canned Heat dragster kit). This photographer's vast collection of online photos of such kits includes some real winners from the era; Murilee says check 'em out.
Vintage Box Art [DWDarby Photography & Design]
Rick Schneider: Revell-Monogram CEO [internal]