Austin Postcard, which has a large collection of vintage postcards from Austin.
You can go way back and see postcards and photos from Austin before the Great Depression. Or you can check out what mid-century Austin looked like. For example, you can look up some pretty neat postcards and photos of the old Mueller Airport. Like this one:
Bueller with an M) was opened in 1936. The fantastic-looking tower and terminal you see in the photo were added in 1961. Mueller airport closed in 1999 and is now home to a mixed-used community. Plans are to keep the tower.