Mid-century modern houses are everywhere...
Savannah, Georgia, has historic houses dating back to the 18th century but it also has enough modern houses to make a modern house tour a worthwhile fundraiser for the American Diabetes Association. Here's an introduction to Savannah's moderns by a writer named Robin Wright Gunn, whose father was one of that city's modern architects.
There are lots of good flash pictures on this website, featuring modern houses for sale in the Philadelphia area.
And here are a bunch of photos of mid-century moderns in Chicago's north shore, which apparently has the same problem with tear-downs that New Canaan has. Denver too, here. -- ta