What are some sources for viewing altitude maps?

The websites FreeMapTools.com, MapDevelopers.com and Altitude.nu each feature free tools that allow users to find the altitude of any point on Earth. Users can search using a variety of criteria, such as city name or street address.

Once a user inputs the data for a particular place, the elevation appears in feet or meters along with the site's longitude and latitude and a map of the surrounding area. The user can zoom in or out to learn more about the locale in question. These tools can give elevation data about a single site or a collection of sites, depending on user preferences.