On pages 265-266 of the 2009 Observer's Handbook is a table listing impact crater sites in North America. I used Google maps to locate satellite imagery of many of them tonight. Very interesting, easy project. Not all are apparent in these views; many are submerged or buried features and are known purely by the physical samples the sites have yielded- sometimes from deeply-drilled cores. But many still bear obvious impact crater features even after millions of years of erosion. In particular, the crown jewel of impact craters, number 3, Barringer Crater; numbers 11 and 12, the Clearwater lakes in Quebec; number 49, the Slate Islands; and even the central feature of Upheval Dome in Utah, number 52 on the list. Hunt some down if you are so inclined.