wpmu_checkAvailableSpace() – Determines if the available space defined by the admin has been exceeded by the user.
wpmu_current_site() – This deprecated function managed much of the site and network loading in multisite.
wpmu_get_blog_allowedthemes() – Deprecated functionality for getting themes allowed on a specific site.
wpmu_signup_blog_notification() – Send a confirmation request email to a user when they sign up for a new site. The new site will not become active until the confirmation link is clicked.
wpmu_signup_user_notification() – Send a confirmation request email to a user when they sign up for a new user account (without signing up for a site at the same time). The user account will not become active until the confirmation link is clicked.
wptexturize_primes() – Implements a logic tree to determine whether or not "7′." represents seven feet, then converts the special char into either a prime char or a closing quote char.
wpview_media_sandbox_styles() – Returns the URLs for CSS files used in an iframe-sandbox’d TinyMCE media view.