Few things serve as better time capsules than vintage postcards. They render a locationidealistically, of course, given that they're sent to far-off friends and relatives with notes about how wonderfully things are going on holidayand freeze it in time. The folks that created ScenePast (which captured and mapped movie locations) have come up with a new app called Americana Road Trip, which contains more than 600 historic cards of various landmarks across the U.S. It allows users to compare a given vista with today's view of the same spot, as well as (somewhat ironically) electronically send someone a missive straight out of the olden days. So go ahead, see how much Columbus Circle has changed in eight decades, and how much Rockefeller Center hasn't.