The redirects framework associates a redirect object to a particular site. Django uses the SITE_ID setting when searching for redirects.
The authentication framework passes the Site object name to the django.contrib.auth.views.login view as the variable {{ site_name }}.
The sitemaps framework uses the domain from the current Site object to fill in the location attributes in the sitemap.
The admin framework uses the current Site object to determine which domain the view or site link is redirected to.
The comments framework uses the sites framework to tie comments to the current SITE_ID setting.
The flatpages framework links the flatpage to specific sites and then uses the SITE_ID setting when displaying the flatpages.
The django.views.defaults.shortcut view uses the domain of the current Site object to calculate the object's URL.
The syndication framework gives the title and description templates access to the current Site object using the variable {{ site }}.