An organization in Google Apps can have multiple domains.
API requests to the Admin SDK require the domain name as a parameter. Ex:
https://apps-apis.google.com/a/feeds/domain/2.0/{domainName}/general/defaultLanguage
Is there a way to programatically list all domains for an organization? If, for example, you wanted to change the lanaguage for all domains in an organization, there doesn't seem to be any way to list/iterate through the domains.